/* Weak references objects for Python. */

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#ifndef Py_WEAKREFOBJECT_H

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#define Py_WEAKREFOBJECT_H

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#ifdef __cplusplus

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extern "C" {

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#endif

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typedef struct _PyWeakReference PyWeakReference;

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/* PyWeakReference is the base struct for the Python ReferenceType, ProxyType,

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* and CallableProxyType.

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*/

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#ifndef Py_LIMITED_API

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struct _PyWeakReference {

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PyObject_HEAD

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/* The object to which this is a weak reference, or Py_None if none.

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* Note that this is a stealth reference: wr_object's refcount is

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* not incremented to reflect this pointer.

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*/

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PyObject *wr_object;

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/* A callable to invoke when wr_object dies, or NULL if none. */

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PyObject *wr_callback;

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/* A cache for wr_object's hash code. As usual for hashes, this is -1

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* if the hash code isn't known yet.

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*/

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Py_hash_t hash;

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/* If wr_object is weakly referenced, wr_object has a doubly-linked NULL-

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* terminated list of weak references to it. These are the list pointers.

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* If wr_object goes away, wr_object is set to Py_None, and these pointers

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* have no meaning then.

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*/

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PyWeakReference *wr_prev;

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PyWeakReference *wr_next;

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};

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#endif

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PyAPI_DATA(PyTypeObject) _PyWeakref_RefType;

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PyAPI_DATA(PyTypeObject) _PyWeakref_ProxyType;

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PyAPI_DATA(PyTypeObject) _PyWeakref_CallableProxyType;

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#define PyWeakref_CheckRef(op) PyObject_TypeCheck(op, &_PyWeakref_RefType)

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#define PyWeakref_CheckRefExact(op) \

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(Py_TYPE(op) == &_PyWeakref_RefType)

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#define PyWeakref_CheckProxy(op) \

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((Py_TYPE(op) == &_PyWeakref_ProxyType) || \

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(Py_TYPE(op) == &_PyWeakref_CallableProxyType))

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#define PyWeakref_Check(op) \

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(PyWeakref_CheckRef(op) || PyWeakref_CheckProxy(op))

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PyAPI_FUNC(PyObject *) PyWeakref_NewRef(PyObject *ob,

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PyObject *callback);

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PyAPI_FUNC(PyObject *) PyWeakref_NewProxy(PyObject *ob,

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PyObject *callback);

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PyAPI_FUNC(PyObject *) PyWeakref_GetObject(PyObject *ref);

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#ifndef Py_LIMITED_API

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PyAPI_FUNC(Py_ssize_t) _PyWeakref_GetWeakrefCount(PyWeakReference *head);

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PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self);

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#endif

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/* Explanation for the Py_REFCNT() check: when a weakref's target is part

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of a long chain of deallocations which triggers the trashcan mechanism,

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clearing the weakrefs can be delayed long after the target's refcount

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has dropped to zero. In the meantime, code accessing the weakref will

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be able to "see" the target object even though it is supposed to be

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unreachable. See issue #16602. */

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#define PyWeakref_GET_OBJECT(ref) \

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(Py_REFCNT(((PyWeakReference *)(ref))->wr_object) > 0 \

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? ((PyWeakReference *)(ref))->wr_object \

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: Py_None)

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#ifdef __cplusplus

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}

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#endif

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#endif /* !Py_WEAKREFOBJECT_H */

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