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The C and C++ Include Header Files

/usr/include/python3.12/cpython/weakrefobject.h


$ cat -n /usr/include/python3.12/cpython/weakrefobject.h

     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	
    35	PyAPI_FUNC(Py_ssize_t) _PyWeakref_GetWeakrefCount(PyWeakReference *head);
    36	
    37	PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self);
    38	
    39	static inline PyObject* PyWeakref_GET_OBJECT(PyObject *ref_obj) {
    40	    PyWeakReference *ref;
    41	    PyObject *obj;
    42	    assert(PyWeakref_Check(ref_obj));
    43	    ref = _Py_CAST(PyWeakReference*, ref_obj);
    44	    obj = ref->wr_object;
    45	    // Explanation for the Py_REFCNT() check: when a weakref's target is part
    46	    // of a long chain of deallocations which triggers the trashcan mechanism,
    47	    // clearing the weakrefs can be delayed long after the target's refcount
    48	    // has dropped to zero.  In the meantime, code accessing the weakref will
    49	    // be able to "see" the target object even though it is supposed to be
    50	    // unreachable.  See issue gh-60806.
    51	    if (Py_REFCNT(obj) > 0) {
    52	        return obj;
    53	    }
    54	    return Py_None;
    55	}
    56	#define PyWeakref_GET_OBJECT(ref) PyWeakref_GET_OBJECT(_PyObject_CAST(ref))