Mercurial > cpython-lru_cache-weakref
diff Include/weakrefobject.h @ 80762:7e771f0363e2 2.7
Issue #16602: When a weakref's target was part of a long deallocation chain, the object could remain reachable through its weakref even though its refcount had dropped to zero.
Thanks to Eugene Toder for diagnosing and reporting the issue.
| author | Antoine Pitrou <solipsis@pitrou.net> |
|---|---|
| date | Sat, 08 Dec 2012 21:15:26 +0100 |
| parents | 86a2679dca46 |
| children | 39e5ab118602 |
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--- a/Include/weakrefobject.h Sat Dec 08 18:01:27 2012 +0200 +++ b/Include/weakrefobject.h Sat Dec 08 21:15:26 2012 +0100 @@ -66,7 +66,17 @@ PyAPI_FUNC(void) _PyWeakref_ClearRef(PyWeakReference *self); -#define PyWeakref_GET_OBJECT(ref) (((PyWeakReference *)(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 #16602. */ + +#define PyWeakref_GET_OBJECT(ref) \ + (Py_REFCNT(((PyWeakReference *)(ref))->wr_object) > 0 \ + ? ((PyWeakReference *)(ref))->wr_object \ + : Py_None) #ifdef __cplusplus