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1: /* Weak references objects for Python. */ 2: 3: #ifndef Py_WEAKREFOBJECT_H 4: #define Py_WEAKREFOBJECT_H 5: #ifdef __cplusplus 6: extern "C" { 7: #endif 8: 9: 10: typedef struct _PyWeakReference PyWeakReference; 11: 12: /* PyWeakReference is the base struct for the Python ReferenceType, ProxyType, 13: * and CallableProxyType. 14: */ 15: #ifndef Py_LIMITED_API 16: struct _PyWeakReference { 17: PyObject_HEAD 18: 19: /* The object to which this is a weak reference, or Py_None if none. 20: * Note that this is a stealth reference: wr_object's refcount is 21: * not incremented to reflect this pointer. 22: */ 23: PyObject *wr_object; 24: 25: /* A callable to invoke when wr_object dies, or NULL if none. */ 26: PyObject *wr_callback; 27: 28: /* A cache for wr_object's hash code. As usual for hashes, this is -1 29: * if the hash code isn't known yet. 30: */ 31: Py_hash_t hash; 32: 33: /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL- 34: * terminated list of weak references to it. These are the list pointers. 35: * If wr_object goes away, wr_object is set to Py_None, and these pointers 36: * have no meaning then. 37: */ 38: PyWeakReference *wr_prev; 39: PyWeakReference *wr_next; 40: }; 41: #endif 42: 43: PyAPI_DATA(PyTypeObject) _PyWeakref_RefType; 44: PyAPI_DATA(PyTypeObject) _PyWeakref_ProxyType; 45: PyAPI_DATA(PyTypeObject) _PyWeakref_CallableProxyType; 46: 47: #define PyWeakref_CheckRef(op) PyObject_TypeCheck(op, &_PyWeakref_RefType) 48: #define PyWeakref_CheckRefExact(op) \ 49: (Py_TYPE(op) == &_PyWeakref_RefType) 50: #define PyWeakref_CheckProxy(op) \ 51: ((Py_TYPE(op) == &_PyWeakref_ProxyType) || \ 52: (Py_TYPE(op) == &_PyWeakref_CallableProxyType)) 53: 54: #define PyWeakref_Check(op) \ 55: (PyWeakref_CheckRef(op) || PyWeakref_CheckProxy(op)) 56: 57: 58: PyAPI_FUNC(PyObject *) PyWeakref_NewRef(PyObject *ob, 59: PyObject *callback); 60: PyAPI_FUNC(PyObject *) PyWeakref_NewProxy(PyObject *ob, 61: PyObject *callback); 62: PyAPI_FUNC(PyObject *) PyWeakref_GetObject(PyObject *ref); 63: 64: #ifndef Py_LIMITED_API 65: PyAPI_FUNC(Py_ssize_t) _PyWeakref_GetWeakrefCount(PyWeakReference *head); 66: 67: PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self); 68: #endif 69: 70: /* Explanation for the Py_REFCNT() check: when a weakref's target is part 71: of a long chain of deallocations which triggers the trashcan mechanism, 72: clearing the weakrefs can be delayed long after the target's refcount 73: has dropped to zero. In the meantime, code accessing the weakref will 74: be able to "see" the target object even though it is supposed to be 75: unreachable. See issue #16602. */ 76: 77: #define PyWeakref_GET_OBJECT(ref) \ 78: (Py_REFCNT(((PyWeakReference *)(ref))->wr_object) > 0 \ 79: ? ((PyWeakReference *)(ref))->wr_object \ 80: : Py_None) 81: 82: 83: #ifdef __cplusplus 84: } 85: #endif 86: #endif /* !Py_WEAKREFOBJECT_H */ 87: