dulwich causes Python's GC to crash

[NuShrike]

Mercurial running Python 2.6.4 in FC13 crashes with
"
python: Modules/gcmodule.c:277: visit_decref: Assertion `gc->gc.gc_refs != 0' failed.
Aborted (core dumped)
"

when Dulwich with at least this commit, or later, is installed:

commit 034b9bf3810c164b648c55a2fde1f575cd5100ae
Author: Dave Borowitz <email address hidden>
Date: Sat Dec 18 18:01:28 2010 +0100

    diff_tree: C implementation of count_blocks.

    Change-Id: I54f903b90533cf821235060aa6f632ea9d4f827a
    Signed-off-by: Jelmer Vernooij <email address hidden>

This commit was found by git bisect between:
commit a383e4501a237cdfff71d971eff0eebf36255d58
Author: Jelmer Vernooij <email address hidden>
Date: Fri Nov 26 16:32:32 2010 +0100

and

commit 44a9af87349237e9a08e4c73896a15499e94e143
Author: Jelmer Vernooij <email address hidden>
Date: Sun Jan 30 18:33:05 2011 +0100

[Jelmer Vernooij (jelmer)]

Thanks for the bug report. Do you perhaps have a simple python script that reproduces it outside of mercurial?

[NuShrike (nushrike)]

No, not really. Best I can do (after going through /usr/lib/python2.6 to find something) is just "hg " anything such as:

hg log
hg status
hg version

etc...

[NuShrike (nushrike)]

This is related to hg-git's use of Dulwich, btw. With the hggit extension for Mercurial off, there is no issue.

[Dave Borowitz (dborowitz)]

I'm unable to reproduce with Python 2.6.5 in Ubuntu Lucid building dulwich and hg-git from head. Can you get a stack trace from the core dump (or just attach it so I can poke around)?

[Ben Axnick (ben-axnick)]

I can confirm this issue on FC14 using Python 2.7.

hg-git was installed via easy_install at version 0.2.5, which pulled Dulwich version 0.7.
When testing Dulwich 0.6.2 via easy_install, the issue did not seem to be present.

I've attached some console output and the results of strace.

[NuShrike (nushrike)]

Attached my strace also.

[NuShrike (nushrike)]

stack trace through gdb; not very useful imo.

[NuShrike (nushrike)]

Fix confirmed for me:
hg-git: c3969cd0baa461401fc1eb6c49ff316a5f7327fc
dulwich: 8a2f5cefc0322bc1396c7d7d265e3af7dbf23378