bpo-32030: Add _PyImport_Fini2() (#4737)

PyImport_ExtendInittab() now uses PyMem_RawRealloc() rather than
PyMem_Realloc(). PyImport_ExtendInittab() can be called before
Py_Initialize() whereas only the PyMem_Raw allocator is supposed to
be used before Py_Initialize().

Add _PyImport_Fini2() to release the memory allocated by
PyImport_ExtendInittab() at exit. PyImport_ExtendInittab() now forces
the usage of the default raw allocator, to be able to release memory
in _PyImport_Fini2().

Don't export these functions anymore to be C API, only to
Py_BUILD_CORE:

* _PyExc_Fini()
* _PyImport_Fini()
* _PyGC_DumpShutdownStats()
* _PyGC_Fini()
* _PyType_Fini()
* _Py_HashRandomization_Fini()

Include/pylifecycle.h

@@ -137,9 +137,18 @@ PyAPI_FUNC(_PyInitError) _Py_HashRandomization_Init(_PyCoreConfig *core_config);
 #endif
 
 /* Various internal finalizers */
-#ifndef Py_LIMITED_API
+
+#ifdef Py_BUILD_CORE
 PyAPI_FUNC(void) _PyExc_Fini(void);
 PyAPI_FUNC(void) _PyImport_Fini(void);
+PyAPI_FUNC(void) _PyImport_Fini2(void);
+PyAPI_FUNC(void) _PyGC_DumpShutdownStats(void);
+PyAPI_FUNC(void) _PyGC_Fini(void);
+PyAPI_FUNC(void) _PyType_Fini(void);
+PyAPI_FUNC(void) _Py_HashRandomization_Fini(void);
+#endif   /* Py_BUILD_CORE */
+
+#ifndef Py_LIMITED_API
 PyAPI_FUNC(void) PyMethod_Fini(void);
 PyAPI_FUNC(void) PyFrame_Fini(void);
 PyAPI_FUNC(void) PyCFunction_Fini(void);
@@ -151,15 +160,11 @@ PyAPI_FUNC(void) PyBytes_Fini(void);
 PyAPI_FUNC(void) PyByteArray_Fini(void);
 PyAPI_FUNC(void) PyFloat_Fini(void);
 PyAPI_FUNC(void) PyOS_FiniInterrupts(void);
-PyAPI_FUNC(void) _PyGC_DumpShutdownStats(void);
-PyAPI_FUNC(void) _PyGC_Fini(void);
 PyAPI_FUNC(void) PySlice_Fini(void);
-PyAPI_FUNC(void) _PyType_Fini(void);
-PyAPI_FUNC(void) _Py_HashRandomization_Fini(void);
 PyAPI_FUNC(void) PyAsyncGen_Fini(void);
 
 PyAPI_FUNC(int) _Py_IsFinalizing(void);
-#endif
+#endif   /* !Py_LIMITED_API */
 
 /* Signals */
 typedef void (*PyOS_sighandler_t)(int);

Modules/main.c

@@ -446,17 +446,18 @@ pymain_optlist_clear(_Py_OptList *list)
     list->options = NULL;
 }
 
-static void
-pymain_free_impl(_PyMain *pymain)
-{
-    _Py_CommandLineDetails *cmdline = &pymain->cmdline;
-    pymain_optlist_clear(&cmdline->warning_options);
-    pymain_optlist_clear(&cmdline->xoptions);
-    PyMem_RawFree(cmdline->command);
 
-    pymain_optlist_clear(&pymain->env_warning_options);
-    Py_CLEAR(pymain->main_importer_path);
+/* Free global variables which cannot be freed in Py_Finalize():
+   configuration options set before Py_Initialize() which should
+   remain valid after Py_Finalize(), since Py_Initialize()/Py_Finalize() can
+   be called multiple times.
 
+   Called with the current memory allocators. */
+static void
+pymain_free_globals(_PyMain *pymain)
+{
+    _PyPathConfig_Clear(&_Py_path_config);
+    _PyImport_Fini2();
     _PyMainInterpreterConfig_Clear(&pymain->config);
 
 #ifdef __INSURE__
@@ -473,6 +474,20 @@ pymain_free_impl(_PyMain *pymain)
 #endif /* __INSURE__ */
 }
 
+
+static void
+pymain_free_pymain(_PyMain *pymain)
+{
+    _Py_CommandLineDetails *cmdline = &pymain->cmdline;
+    pymain_optlist_clear(&cmdline->warning_options);
+    pymain_optlist_clear(&cmdline->xoptions);
+    PyMem_RawFree(cmdline->command);
+
+    pymain_optlist_clear(&pymain->env_warning_options);
+    Py_CLEAR(pymain->main_importer_path);
+
+}
+
 static void
 pymain_free(_PyMain *pymain)
 {
@@ -480,12 +495,12 @@ pymain_free(_PyMain *pymain)
     PyMemAllocatorEx old_alloc;
     _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
 
-    pymain_free_impl(pymain);
+    pymain_free_pymain(pymain);
+    pymain_free_globals(pymain);
 
     PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
 }
 
-
 static int
 pymain_run_main_from_importer(_PyMain *pymain)
 {
@@ -1719,13 +1734,6 @@ pymain_impl(_PyMain *pymain)
         pymain->status = 120;
     }
 
-    /* _PyPathConfig_Clear() cannot be called in Py_FinalizeEx().
-       Py_Initialize() and Py_Finalize() can be called multiple times, but it
-       must not "forget" parameters set by Py_SetProgramName(), Py_SetPath() or
-       Py_SetPythonHome(), whereas _PyPathConfig_Clear() clear all these
-       parameters. */
-    _PyPathConfig_Clear(&_Py_path_config);
-
     return 0;
 }
 

Python/import.c

@@ -30,6 +30,7 @@ static PyObject *extensions = NULL;
 extern struct _inittab _PyImport_Inittab[];
 
 struct _inittab *PyImport_Inittab = _PyImport_Inittab;
+static struct _inittab *inittab_copy = NULL;
 
 /*[clinic input]
 module _imp
@@ -285,6 +286,19 @@ _PyImport_Fini(void)
     }
 }
 
+void
+_PyImport_Fini2(void)
+{
+    /* Use the same memory allocator than PyImport_ExtendInittab(). */
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    /* Free memory allocated by PyImport_ExtendInittab() */
+    PyMem_RawFree(inittab_copy);
+
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+}
+
 /* Helper for sys */
 
 PyObject *
@@ -2233,9 +2247,9 @@ PyInit_imp(void)
 int
 PyImport_ExtendInittab(struct _inittab *newtab)
 {
-    static struct _inittab *our_copy = NULL;
     struct _inittab *p;
-    int i, n;
+    Py_ssize_t i, n;
+    int res = 0;
 
     /* Count the number of entries in both tables */
     for (n = 0; newtab[n].name != NULL; n++)
@@ -2245,19 +2259,35 @@ PyImport_ExtendInittab(struct _inittab *newtab)
     for (i = 0; PyImport_Inittab[i].name != NULL; i++)
         ;
 
+    /* Force default raw memory allocator to get a known allocator to be able
+       to release the memory in _PyImport_Fini2() */
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
     /* Allocate new memory for the combined table */
-    p = our_copy;
-    PyMem_RESIZE(p, struct _inittab, i+n+1);
-    if (p == NULL)
-        return -1;
+    if ((i + n + 1) <= PY_SSIZE_T_MAX / sizeof(struct _inittab)) {
+        size_t size = sizeof(struct _inittab) * (i + n + 1);
+        p = PyMem_RawRealloc(inittab_copy, size);
+    }
+    else {
+        p = NULL;
+    }
+    if (p == NULL) {
+        res = -1;
+        goto done;
+    }
 
-    /* Copy the tables into the new memory */
-    if (our_copy != PyImport_Inittab)
+    /* Copy the tables into the new memory at the first call
+       to PyImport_ExtendInittab(). */
+    if (inittab_copy != PyImport_Inittab) {
         memcpy(p, PyImport_Inittab, (i+1) * sizeof(struct _inittab));
-    PyImport_Inittab = our_copy = p;
-    memcpy(p+i, newtab, (n+1) * sizeof(struct _inittab));
+    }
+    memcpy(p + i, newtab, (n + 1) * sizeof(struct _inittab));
+    PyImport_Inittab = inittab_copy = p;
 
-    return 0;
+done:
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+    return res;
 }
 
 /* Shorthand to add a single entry given a name and a function */