Re: Seek advice about crashes dealing with fonts/faces

[Eli Zaretskii]

> From: "Ludwig, Mark" <ludwig.mark@siemens.com>
> Date: Wed, 8 Apr 2015 22:19:40 +0000
> 
> I've had Emacs 24.4 crash a couple of times this week, and
> wonder if anyone else has seen anything like this or has
> advice about how to make an actionable bug report.
> 
> Emacs is running on Solaris, with the X display pointing to
> eXceed (i.e., Windoze).
> 
> Both of the core dumps have the same 8 functions leading up
> to a bus error (SIGBUS):
> 
> FcPatternObjectFindElt (causes/triggers the SIGBUS)
> FcFontSetList
> FcFontList
> ftfont_list
> xftfont_list
> font_list_entities
> font_find_for_lface
> font_load_for_lface
>  
> Two different functions call font_load_for_lface in my two
> core files, and the rest of the calls are quite different.
> 
> I can't reproduce this at will, but I have a feeling it will
> recur.  Any advice about how to catch it or get better
> diagnostic information for a bug report?

Run Emacs under GDB, and when it crashes, show the full backtrace.
Also, try to figure out which variable is triggering SIGBUS, and show
that as well.

It is best to build Emacs without optimizations and with -g3
command-line switch to the compiler (or its equivalent, if you don't
use GCC), since the backtrace and the other debug info is much more
reliable then.

> Do I already have enough for an actionable bug report?

You do, but adding the information mentioned above would make the
report much more useful.

SIGBUS actually sounds like a fontconfig bug, so if there's a newer
version of that library, perhaps try using it.  Or maybe look for
similar problems in fontconfig bug database, if there is such a thing.