bpo-46613: Add PyType_GetModuleByDef to the public API (GH-31081)

* Make PyType_GetModuleByDef public (remove underscore)

Co-authored-by: Victor Stinner <[email protected]>

Author: encukou

Doc/c-api/type.rst

@@ -149,6 +149,8 @@ Type Objects
    ``Py_TYPE(self)`` may be a *subclass* of the intended class, and subclasses
    are not necessarily defined in the same module as their superclass.
    See :c:type:`PyCMethod` to get the class that defines the method.
+   See :c:func:`PyType_GetModuleByDef` for cases when ``PyCMethod`` cannot
+   be used.
 
    .. versionadded:: 3.9
 
@@ -166,6 +168,21 @@ Type Objects
 
    .. versionadded:: 3.9
 
+.. c:function:: PyObject* PyType_GetModuleByDef(PyTypeObject *type, struct PyModuleDef *def)
+
+   Find the first superclass whose module was created from
+   the given :c:type:`PyModuleDef` *def*, and return that module.
+
+   If no module is found, raises a :py:class:`TypeError` and returns ``NULL``.
+
+   This function is intended to be used together with
+   :c:func:`PyModule_GetState()` to get module state from slot methods (such as
+   :c:member:`~PyTypeObject.tp_init` or :c:member:`~PyNumberMethods.nb_add`)
+   and other places where a method's defining class cannot be passed using the
+   :c:type:`PyCMethod` calling convention.
+
+   .. versionadded:: 3.11
+
 
 Creating Heap-Allocated Types
 .............................

Doc/howto/clinic.rst

@@ -1249,15 +1249,15 @@ The ``defining_class`` converter is not compatible with ``__init__`` and ``__new
 methods, which cannot use the ``METH_METHOD`` convention.
 
 It is not possible to use ``defining_class`` with slot methods.  In order to
-fetch the module state from such methods, use ``_PyType_GetModuleByDef`` to
-look up the module and then :c:func:`PyModule_GetState` to fetch the module
+fetch the module state from such methods, use :c:func:`PyType_GetModuleByDef`
+to look up the module and then :c:func:`PyModule_GetState` to fetch the module
 state.  Example from the ``setattro`` slot method in
 ``Modules/_threadmodule.c``::
 
     static int
     local_setattro(localobject *self, PyObject *name, PyObject *v)
     {
-        PyObject *module = _PyType_GetModuleByDef(Py_TYPE(self), &thread_module);
+        PyObject *module = PyType_GetModuleByDef(Py_TYPE(self), &thread_module);
         thread_module_state *state = get_thread_state(module);
         ...
     }

Doc/whatsnew/3.11.rst

@@ -708,6 +708,11 @@ New Features
 
   (Contributed by Christian Heimes in :issue:`45459`.)
 
+* Added the :c:data:`PyType_GetModuleByDef` function, used to get the module
+  in which a method was defined, in cases where this information is not
+  available directly (via :c:type:`PyCMethod`).
+  (Contributed by Petr Viktorin in :issue:`46613`.)
+
 
 Porting to Python 3.11
 ----------------------

Include/cpython/object.h

@@ -265,7 +265,7 @@ PyAPI_FUNC(PyTypeObject *) _PyType_CalculateMetaclass(PyTypeObject *, PyObject *
 PyAPI_FUNC(PyObject *) _PyType_GetDocFromInternalDoc(const char *, const char *);
 PyAPI_FUNC(PyObject *) _PyType_GetTextSignatureFromInternalDoc(const char *, const char *);
 struct PyModuleDef;
-PyAPI_FUNC(PyObject *) _PyType_GetModuleByDef(PyTypeObject *, struct PyModuleDef *);
+PyAPI_FUNC(PyObject *) PyType_GetModuleByDef(PyTypeObject *, struct PyModuleDef *);
 
 struct _Py_Identifier;
 PyAPI_FUNC(int) PyObject_Print(PyObject *, FILE *, int);

Lib/test/test_capi.py

@@ -1071,15 +1071,15 @@ def test_state_access(self):
                     increment_count(1, 2, 3)
 
     def test_get_module_bad_def(self):
-        # _PyType_GetModuleByDef fails gracefully if it doesn't
+        # PyType_GetModuleByDef fails gracefully if it doesn't
         # find what it's looking for.
         # see bpo-46433
         instance = self.module.StateAccessType()
         with self.assertRaises(TypeError):
             instance.getmodulebydef_bad_def()
 
     def test_get_module_static_in_mro(self):
-        # Here, the class _PyType_GetModuleByDef is looking for
+        # Here, the class PyType_GetModuleByDef is looking for
         # appears in the MRO after a static type (Exception).
         # see bpo-46433
         class Subclass(BaseException, self.module.StateAccessType):

Misc/NEWS.d/next/C API/2022-02-02-17-58-49.bpo-46613.__ZdpH.rst

@@ -0,0 +1,2 @@
+Added function :c:func:`PyType_GetModuleByDef`, which allows accesss to
+module state when a method's defining class is not available.

Modules/_csv.c

@@ -374,7 +374,7 @@ static char *dialect_kws[] = {
 static _csvstate *
 _csv_state_from_type(PyTypeObject *type, const char *name)
 {
-    PyObject *module = _PyType_GetModuleByDef(type, &_csvmodule);
+    PyObject *module = PyType_GetModuleByDef(type, &_csvmodule);
     if (module == NULL) {
         return NULL;
     }

Modules/_functoolsmodule.c

@@ -51,7 +51,7 @@ partial_call(partialobject *pto, PyObject *args, PyObject *kwargs);
 static inline _functools_state *
 get_functools_state_by_type(PyTypeObject *type)
 {
-    PyObject *module = _PyType_GetModuleByDef(type, &_functools_module);
+    PyObject *module = PyType_GetModuleByDef(type, &_functools_module);
     if (module == NULL) {
         return NULL;
     }

Modules/_queuemodule.c

@@ -21,7 +21,7 @@ simplequeue_get_state(PyObject *module)
 }
 static struct PyModuleDef queuemodule;
 #define simplequeue_get_state_by_type(type) \
-    (simplequeue_get_state(_PyType_GetModuleByDef(type, &queuemodule)))
+    (simplequeue_get_state(PyType_GetModuleByDef(type, &queuemodule)))
 
 typedef struct {
     PyObject_HEAD

Modules/_randommodule.c

@@ -99,7 +99,7 @@ get_random_state(PyObject *module)
 static struct PyModuleDef _randommodule;
 
 #define _randomstate_type(type) \
-    (get_random_state(_PyType_GetModuleByDef(type, &_randommodule)))
+    (get_random_state(PyType_GetModuleByDef(type, &_randommodule)))
 
 typedef struct {
     PyObject_HEAD