Changeset 391 for python/trunk/Include/weakrefobject.h

Timestamp:

Mar 19, 2014, 11:31:01 PM (11 years ago)

Author:

dmik

Message:

python: Merge vendor 2.7.6 to trunk.

Location:

python/trunk

Files:

• . (modified) (1 prop)
• Include/weakrefobject.h (modified) (2 diffs)

python/trunk/Include/weakrefobject.h

@@ -50 +50 @@
          (Py_TYPE(op) == &_PyWeakref_CallableProxyType))
 
-/* This macro calls PyWeakref_CheckRef() last since that can involve a
-   function call; this makes it more likely that the function call
-   will be avoided. */
 #define PyWeakref_Check(op) \
         (PyWeakref_CheckRef(op) || PyWeakref_CheckProxy(op))
@@ -67 +64 @@
 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)