[Python-checkins] python/dist/src/Misc NEWS,1.1178,1.1179

tim_one at users.sourceforge.net tim_one at users.sourceforge.net
Sun Oct 31 01:09:24 CEST 2004

Update of /cvsroot/python/python/dist/src/Misc
In directory sc8-pr-cvs1.sourceforge.net:/tmp/cvs-serv22636/Misc

Modified Files:
Log Message:
SF 1055820: weakref callback vs gc vs threads

In cyclic gc, clear weakrefs to unreachable objects before allowing any
Python code (weakref callbacks or __del__ methods) to run.

This is a critical bugfix, affecting all versions of Python since weakrefs
were introduced.  I'll backport to 2.3.

Index: NEWS
RCS file: /cvsroot/python/python/dist/src/Misc/NEWS,v
retrieving revision 1.1178
retrieving revision 1.1179
diff -u -d -r1.1178 -r1.1179
--- NEWS	26 Oct 2004 09:53:46 -0000	1.1178
+++ NEWS	30 Oct 2004 23:09:20 -0000	1.1179
@@ -32,6 +32,17 @@
 Core and builtins
+- Bug #1055820 Cyclic garbage collection was not protecting against that
+  calling a live weakref to a piece of cyclic trash could resurrect an
+  insane mutation of the trash if any Python code ran during gc (via
+  running a dead object's __del__ method, running another callback on a
+  weakref to a dead object, or via any Python code run in any other thread
+  that managed to obtain the GIL while a __del__ or callback was running
+  in the thread doing gc).  The most likely symptom was "impossible"
+  ``AttributeEror`` exceptions, appearing seemingly at random, on weakly
+  referenced objects.  The cure was to clear all weakrefs to unreachable
+  objects before allowing any callbacks to run.
 - Bug #1054139 _PyString_Resize() now invalidates its cached hash value.
 Extension Modules

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