[3.13] gh-118789: Add `PyUnstable_Object_ClearWeakRefsNoCallbacks` (GH-118807) (#120695)

This exposes `PyUnstable_Object_ClearWeakRefsNoCallbacks` as an unstable
C-API function to provide a thread-safe mechanism for clearing weakrefs
without executing callbacks.

Some C-API extensions need to clear weakrefs without calling callbacks,
such as after running finalizers like we do in subtype_dealloc.
Previously they could use `_PyWeakref_ClearRef` on each weakref, but
that's not thread-safe in the free-threaded build.

(cherry picked from commit e8752d7b80775ec2a348cd4bf38cbe26a4a07615)

Co-authored-by: Sam Gross <colesbury@gmail.com>
Co-authored-by: Petr Viktorin <encukou@gmail.com>

2 files changed, 3 insertions, 1 deletions

diff --git a/Include/cpython/object.h b/Include/cpython/object.h
index e624326..6cb2c40 100644
--- a/Include/cpython/object.h
+++ b/Include/cpython/object.h
@@ -288,6 +288,8 @@ PyAPI_FUNC(PyObject **) _PyObject_GetDictPtr(PyObject *);
 PyAPI_FUNC(void) PyObject_CallFinalizer(PyObject *);
 PyAPI_FUNC(int) PyObject_CallFinalizerFromDealloc(PyObject *);
 
+PyAPI_FUNC(void) PyUnstable_Object_ClearWeakRefsNoCallbacks(PyObject *);
+
 /* Same as PyObject_Generic{Get,Set}Attr, but passing the attributes
    dict as the last parameter. */
 PyAPI_FUNC(PyObject *)
diff --git a/Include/internal/pycore_weakref.h b/Include/internal/pycore_weakref.h
index cc6c7ff..94aadb2 100644
--- a/Include/internal/pycore_weakref.h
+++ b/Include/internal/pycore_weakref.h
@@ -109,7 +109,7 @@ extern Py_ssize_t _PyWeakref_GetWeakrefCount(PyObject *obj);
 
 // Clear all the weak references to obj but leave their callbacks uncalled and
 // intact.
-extern void _PyWeakref_ClearWeakRefsExceptCallbacks(PyObject *obj);
+extern void _PyWeakref_ClearWeakRefsNoCallbacks(PyObject *obj);
 
 PyAPI_FUNC(int) _PyWeakref_IsDead(PyObject *weakref);