From 21d563c8594fd218e071c0b22a932b3a3f944595 Mon Sep 17 00:00:00 2001
From: Victor Stinner <vstinner@python.org>
Date: Wed, 18 Mar 2020 22:47:58 +0100
Subject: [PATCH] bpo-38865: Py_FinalizeEx() cannot be called in a
 subinterpreter

Py_FinalizeEx() cannot be called in a subinterpreter anymore.

Fix test_embed.test_audit_subinterpreter(): end subinterpreters.
---
 Doc/c-api/init.rst                            |  5 ++++
 Doc/whatsnew/3.9.rst                          |  3 ++
 .../2020-03-18-22-52-27.bpo-38865.KeRYAu.rst  |  1 +
 Programs/_testembed.c                         | 29 ++++++++++++++-----
 Python/pylifecycle.c                          |  4 +++
 5 files changed, 34 insertions(+), 8 deletions(-)
 create mode 100644 Misc/NEWS.d/next/C API/2020-03-18-22-52-27.bpo-38865.KeRYAu.rst

diff --git a/Doc/c-api/init.rst b/Doc/c-api/init.rst
index f309ad0c03cce9..b98ee1190504e2 100644
--- a/Doc/c-api/init.rst
+++ b/Doc/c-api/init.rst
@@ -290,6 +290,8 @@ Initializing and finalizing the interpreter
    developer might want to free all memory allocated by Python before exiting from
    the application.
 
+   This function cannot be called in a subinterpreter.
+
    **Bugs and caveats:** The destruction of modules and objects in modules is done
    in random order; this may cause destructors (:meth:`__del__` methods) to fail
    when they depend on other objects (even functions) or modules.  Dynamically
@@ -305,6 +307,9 @@ Initializing and finalizing the interpreter
 
    .. versionadded:: 3.6
 
+   .. versionchanged:: 3.9
+      This function cannot be called in a subinterpreter anymore.
+
 .. c:function:: void Py_Finalize()
 
    This is a backwards-compatible version of :c:func:`Py_FinalizeEx` that
diff --git a/Doc/whatsnew/3.9.rst b/Doc/whatsnew/3.9.rst
index 6a6d1ee38c7b60..338cd889fe88a2 100644
--- a/Doc/whatsnew/3.9.rst
+++ b/Doc/whatsnew/3.9.rst
@@ -514,6 +514,9 @@ Build and C API Changes
 
   Extension modules without module state (``m_size <= 0``) are not affected.
 
+* :c:func:`Py_FinalizeEx` cannot be called in a subinterpreter anymore.
+  (Contributed by Victor Stinner in :issue:`38865`.)
+
 
 Deprecated
 ==========
diff --git a/Misc/NEWS.d/next/C API/2020-03-18-22-52-27.bpo-38865.KeRYAu.rst b/Misc/NEWS.d/next/C API/2020-03-18-22-52-27.bpo-38865.KeRYAu.rst
new file mode 100644
index 00000000000000..00152f83f18cde
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2020-03-18-22-52-27.bpo-38865.KeRYAu.rst	
@@ -0,0 +1 @@
+:c:func:`Py_FinalizeEx` cannot be called in a subinterpreter anymore.
diff --git a/Programs/_testembed.c b/Programs/_testembed.c
index 900a4b1d427a6b..110e2d8ae99867 100644
--- a/Programs/_testembed.c
+++ b/Programs/_testembed.c
@@ -1165,7 +1165,7 @@ static volatile int _audit_subinterpreter_interpreter_count = 0;
 
 static int _audit_subinterpreter_hook(const char *event, PyObject *args, void *userdata)
 {
-    printf("%s\n", event);
+    fprintf(stderr, "audit event: %s\n", event);
     if (strcmp(event, "cpython.PyInterpreterState_New") == 0) {
         _audit_subinterpreter_interpreter_count += 1;
     }
@@ -1178,17 +1178,30 @@ static int test_audit_subinterpreter(void)
     PySys_AddAuditHook(_audit_subinterpreter_hook, NULL);
     _testembed_Py_Initialize();
 
-    Py_NewInterpreter();
-    Py_NewInterpreter();
-    Py_NewInterpreter();
+    PyThreadState *mainstate = PyThreadState_Get();
+
+    for (int i=0; i<3; i++) {
+        PyThreadState *substate = Py_NewInterpreter();
+        if (substate == NULL) {
+            fprintf(stderr, "Py_NewInterpreter() failed\n");
+            return 1;
+        }
+        Py_EndInterpreter(substate);
+
+        /* Restore tstate after each Py_EndInterpreter() call. Otherwise the
+           current Python thread state is NULL and so PySys_Audit() does
+           nothing. */
+        PyThreadState_Swap(mainstate);
+    }
 
     Py_Finalize();
 
-    switch (_audit_subinterpreter_interpreter_count) {
-        case 3: return 0;
-        case 0: return -1;
-        default: return _audit_subinterpreter_interpreter_count;
+    printf("audit subinterpreter count: %i\n",
+           _audit_subinterpreter_interpreter_count);
+    if (_audit_subinterpreter_interpreter_count != 3) {
+        return 2;
     }
+    return 0;
 }
 
 typedef struct {
diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index da2bb37af518c3..be4bccc8b97e7e 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -1340,6 +1340,10 @@ Py_FinalizeEx(void)
     PyThreadState *tstate = _PyRuntimeState_GetThreadState(runtime);
     PyInterpreterState *interp = tstate->interp;
 
+    if (!_Py_IsMainInterpreter(tstate)) {
+        Py_FatalError("Py_FinalizeEx cannot be called in a subinterpreter");
+    }
+
     // Wrap up existing "threading"-module-created, non-daemon threads.
     wait_for_thread_shutdown(tstate);