gh-105268: Remove _PyGC_FINALIZED() macro (#105350)

Remove the old private, undocumented and untested _PyGC_FINALIZED()
macro which was kept for backward compatibility with Python 3.8 and
older.

(cherry picked from commit 8ddf0dd)

Author: vstinner

Doc/whatsnew/3.12.rst

@@ -1976,3 +1976,10 @@ Removed
 * Remove ``_use_broken_old_ctypes_structure_semantics_`` flag
   from :mod:`ctypes` module.
   (Contributed by Nikita Sobolev in :gh:`99285`.)
+
+* Remove the old private, undocumented and untested ``_PyGC_FINALIZED()`` macro
+  which was kept for backward compatibility with Python 3.8 and older: use
+  :c:func:`PyObject_GC_IsFinalized()` instead. The `pythoncapi-compat project
+  <https://github.com/python/pythoncapi-compat/>`_ can be used to get this
+  function on Python 3.8 and older.
+  (Contributed by Victor Stinner in :gh:`105268`.)

Include/cpython/objimpl.h

@@ -78,14 +78,6 @@ PyAPI_FUNC(void) PyObject_SetArenaAllocator(PyObjectArenaAllocator *allocator);
 PyAPI_FUNC(int) PyObject_IS_GC(PyObject *obj);
 
 
-/* Code built with Py_BUILD_CORE must include pycore_gc.h instead which
-   defines a different _PyGC_FINALIZED() macro. */
-#ifndef Py_BUILD_CORE
-   // Kept for backward compatibility with Python 3.8
-#  define _PyGC_FINALIZED(o) PyObject_GC_IsFinalized(o)
-#endif
-
-
 // Test if a type supports weak references
 PyAPI_FUNC(int) PyType_SUPPORTS_WEAKREFS(PyTypeObject *type);
 

Misc/NEWS.d/next/C API/2023-06-06-10-57-18.gh-issue-105268.OTJUko.rst

@@ -0,0 +1,3 @@
+Remove the old private, undocumented and untested ``_PyGC_FINALIZED()`` macro
+which was kept for backward compatibility with Python 3.8 and older. Patch by
+Victor Stinner.