fix(cmake): add required emscripten flags (#5298)

* fix(cmake): add required emscripten flags

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Update emscripten.yaml

* fix(cmake): add required emscripten flags to headers target

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix(cmake): incorrect detection of Emscripten

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix(cmake): allow pybind11::headers to be modified

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix(cmake): hide a warning when building the tests standalone

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix(cmake): use explicit variable for is config

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* fix(cmake): go back to ALIAS target

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore: reduce overall diff

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore: reduce overall diff

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* chore: shorten code a bit

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

.github/workflows/emscripten.yaml

@@ -5,6 +5,8 @@ on:
   pull_request:
     branches:
     - master
+    - stable
+    - v*
 
 concurrency:
   group: ${{ github.workflow }}-${{ github.ref }}
@@ -23,8 +25,6 @@ jobs:
     - uses: pypa/cibuildwheel@v2.20
       env:
         PYODIDE_BUILD_EXPORTS: whole_archive
-        CFLAGS: -fexceptions
-        LDFLAGS: -fexceptions
       with:
         package-dir: tests
         only: cp312-pyodide_wasm32

tests/pyproject.toml

@@ -10,6 +10,10 @@ name = "pybind11_tests"
 version = "0.0.1"
 dependencies = ["pytest", "pytest-timeout", "numpy", "scipy"]
 
+[tool.scikit-build]
+# Hide a warning while we also support CMake < 3.15
+cmake.version = ">=3.15"
+
 [tool.scikit-build.cmake.define]
 PYBIND11_FINDPYTHON = true
 

tools/pybind11Common.cmake

@@ -2,7 +2,7 @@
 
 Adds the following targets::
 
-    pybind11::pybind11 - link to headers and pybind11
+    pybind11::pybind11 - link to Python headers and pybind11::headers
     pybind11::module - Adds module links
     pybind11::embed - Adds embed links
     pybind11::lto - Link time optimizations (only if CMAKE_INTERPROCEDURAL_OPTIMIZATION is not set)
@@ -75,6 +75,32 @@ set_property(
   APPEND
   PROPERTY INTERFACE_LINK_LIBRARIES pybind11::pybind11)
 
+# -------------- emscripten requires exceptions enabled -------------
+# _pybind11_no_exceptions is a private mechanism to disable this addition.
+# Please open an issue if you need to use it; it will be removed if no one
+# needs it.
+if(CMAKE_SYSTEM_NAME MATCHES Emscripten AND NOT _pybind11_no_exceptions)
+  if(CMAKE_VERSION VERSION_LESS 3.13)
+    message(WARNING "CMake 3.13+ is required to build for Emscripten. Some flags will be missing")
+  else()
+    if(_is_config)
+      set(_tmp_config_target pybind11::pybind11_headers)
+    else()
+      set(_tmp_config_target pybind11_headers)
+    endif()
+
+    set_property(
+      TARGET ${_tmp_config_target}
+      APPEND
+      PROPERTY INTERFACE_LINK_OPTIONS -fexceptions)
+    set_property(
+      TARGET ${_tmp_config_target}
+      APPEND
+      PROPERTY INTERFACE_COMPILE_OPTIONS -fexceptions)
+    unset(_tmp_config_target)
+  endif()
+endif()
+
 # --------------------------- link helper ---------------------------
 
 add_library(pybind11::python_link_helper IMPORTED INTERFACE ${optional_global})
@@ -329,7 +355,7 @@ function(_pybind11_generate_lto target prefer_thin_lto)
 
     if(CMAKE_SYSTEM_PROCESSOR MATCHES "ppc64le" OR CMAKE_SYSTEM_PROCESSOR MATCHES "mips64")
       # Do nothing
-    elseif(CMAKE_SYSTEM_PROCESSOR MATCHES emscripten)
+    elseif(CMAKE_SYSTEM_NAME MATCHES Emscripten)
       # This compile is very costly when cross-compiling, so set this without checking
       set(PYBIND11_LTO_CXX_FLAGS "-flto${thin}${cxx_append}")
       set(PYBIND11_LTO_LINKER_FLAGS "-flto${thin}${linker_append}")

tools/pybind11Config.cmake.in

@@ -84,7 +84,7 @@ you can either use the basic targets, or use the FindPython tools:
 
   # Python method:
   Python_add_library(MyModule2 src2.cpp)
-  target_link_libraries(MyModule2 pybind11::headers)
+  target_link_libraries(MyModule2 PUBLIC pybind11::headers)
   set_target_properties(MyModule2 PROPERTIES
                                   INTERPROCEDURAL_OPTIMIZATION ON
                                   CXX_VISIBILITY_PRESET ON