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| /* PyWeakReference is the base struct for the Python ReferenceType, ProxyType, | |
| * and CallableProxyType. | |
| */ | |
| struct _PyWeakReference { | |
| PyObject_HEAD | |
| /* The object to which this is a weak reference, or Py_None if none. | |
| * Note that this is a stealth reference: wr_object's refcount is | |
| * not incremented to reflect this pointer. | |
| */ | |
| PyObject *wr_object; | |
| /* A callable to invoke when wr_object dies, or NULL if none. */ | |
| PyObject *wr_callback; | |
| /* A cache for wr_object's hash code. As usual for hashes, this is -1 | |
| * if the hash code isn't known yet. | |
| */ | |
| Py_hash_t hash; | |
| /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL- | |
| * terminated list of weak references to it. These are the list pointers. | |
| * If wr_object goes away, wr_object is set to Py_None, and these pointers | |
| * have no meaning then. | |
| */ | |
| PyWeakReference *wr_prev; | |
| PyWeakReference *wr_next; | |
| vectorcallfunc vectorcall; | |
| }; | |
| PyAPI_FUNC(Py_ssize_t) _PyWeakref_GetWeakrefCount(PyWeakReference *head); | |
| PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self); | |
| static inline PyObject* PyWeakref_GET_OBJECT(PyObject *ref_obj) { | |
| PyWeakReference *ref; | |
| PyObject *obj; | |
| assert(PyWeakref_Check(ref_obj)); | |
| ref = _Py_CAST(PyWeakReference*, ref_obj); | |
| obj = ref->wr_object; | |
| // Explanation for the Py_REFCNT() check: when a weakref's target is part | |
| // of a long chain of deallocations which triggers the trashcan mechanism, | |
| // clearing the weakrefs can be delayed long after the target's refcount | |
| // has dropped to zero. In the meantime, code accessing the weakref will | |
| // be able to "see" the target object even though it is supposed to be | |
| // unreachable. See issue gh-60806. | |
| if (Py_REFCNT(obj) > 0) { | |
| return obj; | |
| } | |
| return Py_None; | |
| } | |