bpo-32030: Rework memory allocators (#4625)

* Fix _PyMem_SetupAllocators("debug"): always restore allocators to
  the defaults, rather than only caling _PyMem_SetupDebugHooks().
* Add _PyMem_SetDefaultAllocator() helper to set the "default"
  allocator.
* Add _PyMem_GetAllocatorsName(): get the name of the allocators
* main() now uses debug hooks on memory allocators if Py_DEBUG is
  defined, rather than calling directly malloc()
* Document default memory allocators in C API documentation
* _Py_InitializeCore() now fails with a fatal user error if
  PYTHONMALLOC value is an unknown memory allocator, instead of
  failing with a fatal internal error.
* Add new tests on the PYTHONMALLOC environment variable
* Add support.with_pymalloc()
* Add the _testcapi.WITH_PYMALLOC constant and expose it as
   support.with_pymalloc().
* sysconfig.get_config_var('WITH_PYMALLOC') doesn't work on Windows, so
   replace it with support.with_pymalloc().
* pythoninfo: add _testcapi collector for pymem

2 files changed, 20 insertions, 8 deletions

diff --git a/Python/pylifecycle.c b/Python/pylifecycle.c
index b89cbc8..01f314e 100644
--- a/Python/pylifecycle.c
+++ b/Python/pylifecycle.c
@@ -630,7 +630,7 @@ _Py_InitializeCore(const _PyCoreConfig *config)
     }
 
     if (_PyMem_SetupAllocators(core_config.allocator) < 0) {
-        return _Py_INIT_ERR("Unknown PYTHONMALLOC allocator");
+        return _Py_INIT_USER_ERR("Unknown PYTHONMALLOC allocator");
     }
 
     if (_PyRuntime.initialized) {
diff --git a/Python/pystate.c b/Python/pystate.c
index ecf921d..0fb8ed0 100644
--- a/Python/pystate.c
+++ b/Python/pystate.c
@@ -35,8 +35,8 @@ to avoid the expense of doing their own locking).
 extern "C" {
 #endif
 
-_PyInitError
-_PyRuntimeState_Init(_PyRuntimeState *runtime)
+static _PyInitError
+_PyRuntimeState_Init_impl(_PyRuntimeState *runtime)
 {
     memset(runtime, 0, sizeof(*runtime));
 
@@ -59,14 +59,26 @@ _PyRuntimeState_Init(_PyRuntimeState *runtime)
     return _Py_INIT_OK();
 }
 
+_PyInitError
+_PyRuntimeState_Init(_PyRuntimeState *runtime)
+{
+    /* Force default allocator, since _PyRuntimeState_Fini() must
+       use the same allocator than this function. */
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+
+    _PyInitError err = _PyRuntimeState_Init_impl(runtime);
+
+    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
+    return err;
+}
+
 void
 _PyRuntimeState_Fini(_PyRuntimeState *runtime)
 {
-    /* Use the same memory allocator than _PyRuntimeState_Init() */
-    PyMemAllocatorEx old_alloc, raw_alloc;
-    PyMem_GetAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
-    _PyMem_GetDefaultRawAllocator(&raw_alloc);
-    PyMem_SetAllocator(PYMEM_DOMAIN_RAW, &raw_alloc);
+    /* Force the allocator used by _PyRuntimeState_Init(). */
+    PyMemAllocatorEx old_alloc;
+    _PyMem_SetDefaultAllocator(PYMEM_DOMAIN_RAW, &old_alloc);
 
     if (runtime->interpreters.mutex != NULL) {
         PyThread_free_lock(runtime->interpreters.mutex);