Re: GDB cannot access memory after Emacs abort

[Stephen Berman <Stephen.Berman@gmx.net>]

On Tue, 13 Nov 2007 15:14:58 -0800 Michael Snyder <msnyder@specifix.com> wrote:

> On Tue, 2007-11-13 at 23:29 +0100, Stephen Berman wrote:
[...]
>> But as I pointed out in my followup to Jim Blandy, the lockup only
>> happens when emacs aborts while running under gdb; starting emacs
>> directly from the shell and inducing the abort does not lock up the
>> desktop.
>
> Hoping you have seen my other replies, I believe we understand
> why this happens.
>
> I do have a suggestion.
>
> Run gdb from a non-GUI terminal, eg. a virtual console.
>
> For example, launch emacs normally, WITHOUT gdb, from gnome/kde/gtk/X.
> Then go to a virtual console, use 'ps' to determine the process id of
> emacs, then start gdb and use the "attach" command to get control of
> emacs from gdb.
>
> Now return to the GUI console, and make emacs crash.
>
> When you return to the virtual console, you should be able to debug.

Thanks for this suggestion, it worked.  Here's the backtrace:

#0  abort () at emacs.c:431
#1  0xb798526a in g_logv () from /usr/lib/libglib-2.0.so.0
#2  0xb79852a9 in g_log () from /usr/lib/libglib-2.0.so.0
#3  0xb7985320 in g_assert_warning () from /usr/lib/libglib-2.0.so.0
#4  0xb7c7b195 in gtk_container_propagate_expose () from /usr/lib/libgtk-x11-2.0.so.0
#5  0xb7c7b1c1 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#6  0x085c2d00 in ?? ()
#7  0x086c0a08 in ?? ()
#8  0x087c31f0 in ?? ()
#9  0xb7d23b6a in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#10 0xb7f3aff4 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#11 0x085c2d00 in ?? ()
#12 0xbfef82a8 in ?? ()
#13 0xb7cf4b42 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#14 0x086c0a08 in ?? ()
#15 0xbfef82e8 in ?? ()
#16 0xb7c7b1a0 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#17 0xbfef82e8 in ?? ()
#18 0x0000001e in ?? ()
#19 0x40000036 in ?? ()
#20 0xbfef82b8 in ?? ()
#21 0xb7f3aff4 in ?? () from /usr/lib/libgtk-x11-2.0.so.0
#22 0x085c2d00 in ?? ()
#23 0x085c2d00 in ?? ()
#24 0xbfef82c8 in ?? ()
#25 0xb7c7bbe7 in gtk_container_forall () from /usr/lib/libgtk-x11-2.0.so.0
Backtrace stopped: previous frame inner to this frame (corrupt stack?)

I don't know if this is useful to you or any other gdb hacker.  I don't
have the GTK+ sources installed.  Maybe someone who does can reproduce
the abort and get a more informative backtrace.  In any case, the fact
that I have gotten a backtrace now evidently absolves GDB of the
suspicion that it had a bug preventing a backtrace :-).  And since the
Emacs bug causing the abort was already fixed, and the issue of the
desktop lockup has been explained, I guess we can declare this issue
closed, unless someone thinks the above backtrace is still reason for
concern.

Steve Berman