GNU bug report logs - #23726
25.0.94; emacs 25.0.94 crashes

Previous Next

Full log

View this message in rfc822 format

From: Florian Weimer <fweimer <at> redhat.com>
To: Paul Eggert <eggert <at> cs.ucla.edu>, Jan Synáček <jsynacek <at> redhat.com>
Cc: 23726 <at> debbugs.gnu.org
Subject: bug#23726: emacs 25.0.94 crashes
Date: Wed, 8 Jun 2016 20:34:58 +0200

On 06/08/2016 07:32 PM, Paul Eggert wrote:
> Has Rawhide incorporated some of Florian Weimer's malloc patches? If so,
> this is almost surely causing the problem. I will CC: Florian to give
> him a heads-up. See:
>
> https://sourceware.org/ml/libc-alpha/2016-06/msg00211.html

That's not the patch, it's not even in upstream master.  If that patch 
was in, you wouldn't see the problem anymore because Emacs' internal 
malloc would be used.

The problem is that the realloc implementation for dumped chunks is 
incorrect; that bit is already in glibc master and rawhide.  I think I 
can see what is wrong: The size computation for the old chunk size in 
realloc is wrong, and the trailing sizeof (size_t) bytes are not copied. 
 Fortunately, it's not a conceptual problem with the heap rewriter.

> I am surprised that you can use valgrind.

The valgrind failure is typical of what you get with a dumped Emacs. 
valgrind intercepts realloc and returns 0 because an off-heap pointer is 
detected.

Florian

Previous Next

GNU bug tracking system
Copyright (C) 1999 Darren O. Benham, 1997,2003 nCipher Corporation Ltd, 1994-97 Ian Jackson.