1 #ifndef Py_CPYTHON_WEAKREFOBJECT_H
2 # error "this header file must not be included directly"
3 #endif
4
5 /* PyWeakReference is the base struct for the Python ReferenceType, ProxyType,
6 * and CallableProxyType.
7 */
8 struct _PyWeakReference {
9 PyObject_HEAD
10
11 /* The object to which this is a weak reference, or Py_None if none.
12 * Note that this is a stealth reference: wr_object's refcount is
13 * not incremented to reflect this pointer.
14 */
15 PyObject *wr_object;
16
17 /* A callable to invoke when wr_object dies, or NULL if none. */
18 PyObject *wr_callback;
19
20 /* A cache for wr_object's hash code. As usual for hashes, this is -1
21 * if the hash code isn't known yet.
22 */
23 Py_hash_t hash;
24
25 /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL-
26 * terminated list of weak references to it. These are the list pointers.
27 * If wr_object goes away, wr_object is set to Py_None, and these pointers
28 * have no meaning then.
29 */
30 PyWeakReference *wr_prev;
31 PyWeakReference *wr_next;
32 vectorcallfunc vectorcall;
33
34 #ifdef Py_GIL_DISABLED
35 /* Pointer to the lock used when clearing in free-threaded builds.
36 * Normally this can be derived from wr_object, but in some cases we need
37 * to lock after wr_object has been set to Py_None.
38 */
39 PyMutex *weakrefs_lock;
40 #endif
41 };
42
43 PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self);
44
PyWeakref_GET_OBJECT(PyObject * ref_obj)45 Py_DEPRECATED(3.13) static inline PyObject* PyWeakref_GET_OBJECT(PyObject *ref_obj)
46 {
47 PyWeakReference *ref;
48 PyObject *obj;
49 assert(PyWeakref_Check(ref_obj));
50 ref = _Py_CAST(PyWeakReference*, ref_obj);
51 obj = ref->wr_object;
52 // Explanation for the Py_REFCNT() check: when a weakref's target is part
53 // of a long chain of deallocations which triggers the trashcan mechanism,
54 // clearing the weakrefs can be delayed long after the target's refcount
55 // has dropped to zero. In the meantime, code accessing the weakref will
56 // be able to "see" the target object even though it is supposed to be
57 // unreachable. See issue gh-60806.
58 if (Py_REFCNT(obj) > 0) {
59 return obj;
60 }
61 return Py_None;
62 }
63 #define PyWeakref_GET_OBJECT(ref) PyWeakref_GET_OBJECT(_PyObject_CAST(ref))
64