Bugs item #1377858, was opened at 2005-12-10 21:20 Message generated for change (Comment added) made by arigo You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1377858&group_id=5470
Please note that this message will contain a full copy of the comment thread, including the initial issue submission, for this request, not just the latest update. Category: Python Interpreter Core Group: Python 2.5 Status: Open Resolution: None Priority: 7 Submitted By: Carl Friedrich Bolz (cfbolz) Assigned to: Michael Hudson (mwh) Summary: segfaults when using __del__ and weakrefs Initial Comment: You can segfault Python by creating a weakref to an object in its __del__ method, storing it somewhere and then trying to dereference the weakref afterwards. the attached file shows the described behaviour. ---------------------------------------------------------------------- >Comment By: Armin Rigo (arigo) Date: 2006-08-12 11:31 Message: Logged In: YES user_id=4771 The clear_weakref(*list) only clears the first weakref to the object. You need a while loop in your patch. (attached proposed fix) Now we're left with fixing the same bug in old-style classes (surprize surprize), and turning the crasher into a test. ---------------------------------------------------------------------- Comment By: Brett Cannon (bcannon) Date: 2006-06-29 17:36 Message: Logged In: YES user_id=357491 So after staring at this crasher it seemed to me to be that clearing the new weakrefs w/o calling their finalizers after calling the object's finalizer was the best solution. I couldn't think of any other good way to communicate to the new weakrefs that the object they refer to was no longer viable memory without doing clear_weakref() work by hand. Attached is a patch to do this. Michael, can you have a look? ---------------------------------------------------------------------- Comment By: Georg Brandl (birkenfeld) Date: 2006-01-10 19:29 Message: Logged In: YES user_id=1188172 Added to outstanding_crashes.py. ---------------------------------------------------------------------- Comment By: Michael Hudson (mwh) Date: 2006-01-09 11:58 Message: Logged In: YES user_id=6656 Hmm, maybe the referenced mayhem is more to do with clearing __dict__ than calling __del__. What breaks if we do things in this order: 1. call __del__ 2. clear weakrefs 3. clear __dict__ ? ---------------------------------------------------------------------- Comment By: Michael Hudson (mwh) Date: 2006-01-09 11:54 Message: Logged In: YES user_id=6656 Hmm, I was kind of hoping this report would get more attention. The problem is obvious if you read typeobject.c around line 660: the weakref list is cleared before __del__ is called, so any weakrefs added during the execution of __del__ are never informed of the object's death. One fix for this would be to clear the weakref list _after_ calling __del__ but that led to other mayhem in ways I haven't boethered to understand <wink> (see SF bug #742911). I guess we could just clear out any weakrefs created in __del__ without calling their callbacks. ---------------------------------------------------------------------- You can respond by visiting: https://sourceforge.net/tracker/?func=detail&atid=105470&aid=1377858&group_id=5470 _______________________________________________ Python-bugs-list mailing list Unsubscribe: http://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
