Re: [Texmacs-dev] GCC-3.2 segfault debugging update

[David Allouche]

On Fri, Nov 29, 2002 at 01:59:32AM +0300, Igor V. Kovalenko wrote:
> David Allouche wrote:
> >Guile does raise a big mass of false positives in its stack walking
> >code. However Valgrind has a nice suppression feature which make it
> >easy to weed them out. My suppression file is attached to this email,
> >it also suppress some Xlib hits which seem caused by problems in my
> >Xlib installation and/or in Valgrind.
> 
> I tried to track guile false positives some time ago :) Some led me to
> uninitialized values in TeXmacs own code. But they should be detectable
> anyway. It's nice you have these suppressions ready.

Actually, my suppression file leaves much to be desired. Generally,
suppressions should be as restrictive as possible to try to avoid
false negatives. But I just wanted to get away with that quickly
(also, I had not read the doc at that moment) so I made very generic
suppressions... not very elegant.

> >I also was able to reproduce the autosave crash. It seems to be caused
> >by multiple destruction of a tree object when returning from an inner
> >"tm_writer::write" call directly into "tm_data_rep::save_tree(string,
> >tree, bool)", but only occurs if save_tree is called from
> >"tm_data_rep::auto_save()"! Though such a return path does not exist
> >in the code but the optimizer reschedule things.
> 
> This should not happen if I correctly understand the thing of side effects.
> I see this return path as it should be created by GCC bug.

I think at this point it is clear that it is a g++ bug. But it might
be possible to find an appropriate no-op transformation of the code
which would work around the bug. Even if that is not the case, we want
this problem to be fixed someday, so we want to produce a simple
crash-test for the gcc hackers to test (and for our configure script
too).

> Do you use GCC-3.2.1 (release) version?

address@hidden texmacs$ g++-3.2 --version
g++-3.2 (GCC) 3.2.1 20020924 (Debian prerelease)

I am installing g++3.2.1 (from Unstable) right now.

-- 
David Allouche         | GNU TeXmacs -- Writing is a pleasure
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TeXmacs is NOT a LaTeX front-end and is unrelated to emacs.