gh-141004: Document PyType_SUPPORTS_WEAKREFS (GH-141408)

Co-authored-by: Stan Ulbrych <89152624+StanFromIreland@users.noreply.github.com>

Doc/c-api/type.rst

@@ -195,12 +195,14 @@ Type Objects
    before initialization) and should be paired with :c:func:`PyObject_Free` in
    :c:member:`~PyTypeObject.tp_free`.
 
+
 .. c:function:: PyObject* PyType_GenericNew(PyTypeObject *type, PyObject *args, PyObject *kwds)
 
    Generic handler for the :c:member:`~PyTypeObject.tp_new` slot of a type
    object.  Creates a new instance using the type's
    :c:member:`~PyTypeObject.tp_alloc` slot and returns the resulting object.
 
+
 .. c:function:: int PyType_Ready(PyTypeObject *type)
 
    Finalize a type object.  This should be called on all type objects to finish
@@ -217,6 +219,7 @@ Type Objects
        GC protocol itself by at least implementing the
        :c:member:`~PyTypeObject.tp_traverse` handle.
 
+
 .. c:function:: PyObject* PyType_GetName(PyTypeObject *type)
 
    Return the type's name. Equivalent to getting the type's
@@ -224,6 +227,7 @@ Type Objects
 
    .. versionadded:: 3.11
 
+
 .. c:function:: PyObject* PyType_GetQualName(PyTypeObject *type)
 
    Return the type's qualified name. Equivalent to getting the
@@ -239,6 +243,7 @@ Type Objects
 
    .. versionadded:: 3.13
 
+
 .. c:function:: PyObject* PyType_GetModuleName(PyTypeObject *type)
 
    Return the type's module name. Equivalent to getting the
@@ -246,6 +251,7 @@ Type Objects
 
    .. versionadded:: 3.13
 
+
 .. c:function:: void* PyType_GetSlot(PyTypeObject *type, int slot)
 
    Return the function pointer stored in the given slot. If the
@@ -262,6 +268,7 @@ Type Objects
       :c:func:`PyType_GetSlot` can now accept all types.
       Previously, it was limited to :ref:`heap types <heap-types>`.
 
+
 .. c:function:: PyObject* PyType_GetModule(PyTypeObject *type)
 
    Return the module object associated with the given type when the type was
@@ -281,6 +288,7 @@ Type Objects
 
    .. versionadded:: 3.9
 
+
 .. c:function:: void* PyType_GetModuleState(PyTypeObject *type)
 
    Return the state of the module object associated with the given type.
@@ -295,6 +303,7 @@ Type Objects
 
    .. versionadded:: 3.9
 
+
 .. c:function:: PyObject* PyType_GetModuleByDef(PyTypeObject *type, struct PyModuleDef *def)
 
    Find the first superclass whose module was created from
@@ -314,6 +323,7 @@ Type Objects
 
    .. versionadded:: 3.11
 
+
 .. c:function:: int PyType_GetBaseByToken(PyTypeObject *type, void *token, PyTypeObject **result)
 
    Find the first superclass in *type*'s :term:`method resolution order` whose
@@ -332,6 +342,7 @@ Type Objects
 
    .. versionadded:: 3.14
 
+
 .. c:function:: int PyUnstable_Type_AssignVersionTag(PyTypeObject *type)
 
    Attempt to assign a version tag to the given type.
@@ -342,6 +353,16 @@ Type Objects
    .. versionadded:: 3.12
 
 
+.. c:function:: int PyType_SUPPORTS_WEAKREFS(PyTypeObject *type)
+
+   Return true if instances of *type* support creating weak references, false
+   otherwise. This function always succeeds. *type* must not be ``NULL``.
+
+   .. seealso::
+      * :ref:`weakrefobjects`
+      * :py:mod:`weakref`
+
+
 Creating Heap-Allocated Types
 .............................
 
@@ -390,6 +411,7 @@ The following functions and structs are used to create
 
    .. versionadded:: 3.12
 
+
 .. c:function:: PyObject* PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
 
    Equivalent to ``PyType_FromMetaclass(NULL, module, spec, bases)``.
@@ -416,6 +438,7 @@ The following functions and structs are used to create
       Creating classes whose metaclass overrides
       :c:member:`~PyTypeObject.tp_new` is no longer allowed.
 
+
 .. c:function:: PyObject* PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)
 
    Equivalent to ``PyType_FromMetaclass(NULL, NULL, spec, bases)``.
@@ -437,6 +460,7 @@ The following functions and structs are used to create
       Creating classes whose metaclass overrides
       :c:member:`~PyTypeObject.tp_new` is no longer allowed.
 
+
 .. c:function:: PyObject* PyType_FromSpec(PyType_Spec *spec)
 
    Equivalent to ``PyType_FromMetaclass(NULL, NULL, spec, NULL)``.
@@ -457,6 +481,7 @@ The following functions and structs are used to create
       Creating classes whose metaclass overrides
       :c:member:`~PyTypeObject.tp_new` is no longer allowed.
 
+
 .. c:function:: int PyType_Freeze(PyTypeObject *type)
 
    Make a type immutable: set the :c:macro:`Py_TPFLAGS_IMMUTABLETYPE` flag.
@@ -628,6 +653,7 @@ The following functions and structs are used to create
       * :c:data:`Py_tp_token` (for clarity, prefer :c:data:`Py_TP_USE_SPEC`
         rather than ``NULL``)
 
+
 .. c:macro:: Py_tp_token
 
    A :c:member:`~PyType_Slot.slot` that records a static memory layout ID

Doc/c-api/weakref.rst

@@ -45,6 +45,10 @@ as much as it can.
    weakly referenceable object, or if *callback* is not callable, ``None``, or
    ``NULL``, this will return ``NULL`` and raise :exc:`TypeError`.
 
+   .. seealso::
+      :c:func:`PyType_SUPPORTS_WEAKREFS` for checking if *ob* is weakly
+      referenceable.
+
 
 .. c:function:: PyObject* PyWeakref_NewProxy(PyObject *ob, PyObject *callback)
 
@@ -57,6 +61,10 @@ as much as it can.
    is not a weakly referenceable object, or if *callback* is not callable,
    ``None``, or ``NULL``, this will return ``NULL`` and raise :exc:`TypeError`.
 
+   .. seealso::
+      :c:func:`PyType_SUPPORTS_WEAKREFS` for checking if *ob* is weakly
+      referenceable.
+
 
 .. c:function:: int PyWeakref_GetRef(PyObject *ref, PyObject **pobj)