Bugs item #1377858, was opened at 2005-12-10 13:20 Message generated for change (Comment added) made by bcannon 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: Closed Resolution: Accepted Priority: 9 Private: No Submitted By: Carl Friedrich Bolz (cfbolz) Assigned to: Brett Cannon (bcannon) 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: Brett Cannon (bcannon) Date: 2007-01-23 15:22 Message: Logged In: YES user_id=357491 Originator: NO rev. 53533 (for 25-maint) and rev. 53535 (trunk) have the patch with an improved comment. Py3K should eventually have its crasher file for this test deleted since classic classes will no longer be an issue. ---------------------------------------------------------------------- Comment By: Martin v. Löwis (loewis) Date: 2007-01-23 13:26 Message: Logged In: YES user_id=21627 Originator: NO The first comment has a non-sensical (to me) phrase: "rely on part of theof the object". Otherwise, it looks fine to me. Please apply, if you can, before 2.5c1. ---------------------------------------------------------------------- Comment By: Brett Cannon (bcannon) Date: 2007-01-17 10:38 Message: Logged In: YES user_id=357491 Originator: NO I have just been waiting on someone to do a final code review on it. As soon as someone else signs off I will commit it. ---------------------------------------------------------------------- Comment By: Neal Norwitz (nnorwitz) Date: 2007-01-16 23:02 Message: Logged In: YES user_id=33168 Originator: NO Brett, Michael, Armin, can we get this patch checked in for 2.5.1? ---------------------------------------------------------------------- Comment By: Brett Cannon (bcannon) Date: 2006-08-19 21:31 Message: Logged In: YES user_id=357491 After finally figuring out where *list was made NULL (and adding a comment about it where it occurs), I added a test to test_weakref.py . Didn't try to tackle classic classes. ---------------------------------------------------------------------- Comment By: Armin Rigo (arigo) Date: 2006-08-12 04:31 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 10:36 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 11:29 Message: Logged In: YES user_id=1188172 Added to outstanding_crashes.py. ---------------------------------------------------------------------- Comment By: Michael Hudson (mwh) Date: 2006-01-09 03:58 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 03:54 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
