1+ /* Copyright (c) 2019, Oracle and/or its affiliates.
2+ * Copyright (C) 1996-2017 Python Software Foundation
3+ *
4+ * Licensed under the PYTHON SOFTWARE FOUNDATION LICENSE VERSION 2
5+ */
6+ /* Weak references objects for Python. */
7+
8+ #ifndef Py_WEAKREFOBJECT_H
9+ #define Py_WEAKREFOBJECT_H
10+ #ifdef __cplusplus
11+ extern "C" {
12+ #endif
13+
14+
15+ typedef struct _PyWeakReference PyWeakReference ;
16+
17+ /* PyWeakReference is the base struct for the Python ReferenceType, ProxyType,
18+ * and CallableProxyType.
19+ */
20+ #ifndef Py_LIMITED_API
21+ struct _PyWeakReference {
22+ PyObject_HEAD
23+
24+ /* The object to which this is a weak reference, or Py_None if none.
25+ * Note that this is a stealth reference: wr_object's refcount is
26+ * not incremented to reflect this pointer.
27+ */
28+ PyObject * wr_object ;
29+
30+ /* A callable to invoke when wr_object dies, or NULL if none. */
31+ PyObject * wr_callback ;
32+
33+ /* A cache for wr_object's hash code. As usual for hashes, this is -1
34+ * if the hash code isn't known yet.
35+ */
36+ Py_hash_t hash ;
37+
38+ /* If wr_object is weakly referenced, wr_object has a doubly-linked NULL-
39+ * terminated list of weak references to it. These are the list pointers.
40+ * If wr_object goes away, wr_object is set to Py_None, and these pointers
41+ * have no meaning then.
42+ */
43+ PyWeakReference * wr_prev ;
44+ PyWeakReference * wr_next ;
45+ };
46+ #endif
47+
48+ PyAPI_DATA (PyTypeObject ) _PyWeakref_RefType ;
49+ PyAPI_DATA (PyTypeObject ) _PyWeakref_ProxyType ;
50+ PyAPI_DATA (PyTypeObject ) _PyWeakref_CallableProxyType ;
51+
52+ #define PyWeakref_CheckRef (op ) PyObject_TypeCheck(op, &_PyWeakref_RefType)
53+ #define PyWeakref_CheckRefExact (op ) \
54+ (Py_TYPE(op) == &_PyWeakref_RefType)
55+ #define PyWeakref_CheckProxy (op ) \
56+ ((Py_TYPE(op) == &_PyWeakref_ProxyType) || \
57+ (Py_TYPE(op) == &_PyWeakref_CallableProxyType))
58+
59+ #define PyWeakref_Check (op ) \
60+ (PyWeakref_CheckRef(op) || PyWeakref_CheckProxy(op))
61+
62+
63+ PyAPI_FUNC (PyObject * ) PyWeakref_NewRef (PyObject * ob ,
64+ PyObject * callback );
65+ PyAPI_FUNC (PyObject * ) PyWeakref_NewProxy (PyObject * ob ,
66+ PyObject * callback );
67+ PyAPI_FUNC (PyObject * ) PyWeakref_GetObject (PyObject * ref );
68+
69+ #ifndef Py_LIMITED_API
70+ PyAPI_FUNC (Py_ssize_t ) _PyWeakref_GetWeakrefCount (PyWeakReference * head );
71+
72+ PyAPI_FUNC (void ) _PyWeakref_ClearRef (PyWeakReference * self );
73+ #endif
74+
75+ /* Explanation for the Py_REFCNT() check: when a weakref's target is part
76+ of a long chain of deallocations which triggers the trashcan mechanism,
77+ clearing the weakrefs can be delayed long after the target's refcount
78+ has dropped to zero. In the meantime, code accessing the weakref will
79+ be able to "see" the target object even though it is supposed to be
80+ unreachable. See issue #16602. */
81+
82+ #define PyWeakref_GET_OBJECT (ref ) \
83+ (Py_REFCNT(((PyWeakReference *)(ref))->wr_object) > 0 \
84+ ? ((PyWeakReference *)(ref))->wr_object \
85+ : Py_None)
86+
87+
88+ #ifdef __cplusplus
89+ }
90+ #endif
91+ #endif /* !Py_WEAKREFOBJECT_H */
0 commit comments