Viewing file:  weakrefobject.h (1.98 KB) -rw-r--r--
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#ifndef Py_CPYTHON_WEAKREFOBJECT_H
# error "this header file must not be included directly"
#endif
/* 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;
}
#define PyWeakref_GET_OBJECT(ref) PyWeakref_GET_OBJECT(_PyObject_CAST(ref))
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