C API: _PyObject_VisitManagedDict() function should be public #107073

tl; dr: _PyObject_VisitManagedDict() and _PyObject_ClearManagedDict() function should be public.

If a C extension implements a type as a heap type, the type must support the GC protocol: it must implement visit and clear functions, and the dealloc function must DECREF the type.

It seems like if a heap type uses the new Py_TPFLAGS_MANAGED_DICT flag, the visit function must call _PyObject_VisitManagedDict() and the clear function must call _PyObject_ClearManagedDict(). Correct me if I'm wrong.

Problem: _PyObject_VisitManagedDict() and _PyObject_ClearManagedDict() functions are private. IMO they must be public.

Either Py_TPFLAGS_MANAGED_DICT flag must be private, or it should be public and all related helper functions should be public as well.

Py_TPFLAGS_MANAGED_DICT was added to Python 3.11.

_PyObject_VisitManagedDict() and _PyObject_ClearManagedDict() functions were added to Python 3.12.

In Python 3.12, typing.TypeVar, typing.ParamSpec, typing.TypeVarTuple are implemented with Py_TPFLAGS_MANAGED_DICT (and use the 2 helper functions).

In Python 3.13, _asyncio.Future and _asyncio.Task are also implemented with Py_TPFLAGS_MANAGED_DICT (and use the 2 helper functions).

Note: In Objects/typeobject.c, subtype_traverse() calls _PyObject_VisitManagedDict() in some cases, and subtype_clear() calls _PyObject_ClearManagedDict() in some cases.

Linked PRs

• gh-107073: Make PyObject_VisitManagedDict() public #108763
• gh-107073: Mention pythoncapi-compat for PyObject_VisitManagedDict() #110291
• gh-107073: fix relevant typo in PyObject_ClearManagedDict #140032
• [3.14] gh-107073: fix relevant typo in PyObject_ClearManagedDict (GH-140032) #140033
• [3.13] gh-107073: fix relevant typo in PyObject_ClearManagedDict (GH-140032) #140034