bug#23704: 25.1.50; Emacs crash in syntax.c

[Eli Zaretskii <eliz@gnu.org>]

> From: vincent.belaiche@gmail.com (Vincent Belaïche)
> Date: Mon, 06 Jun 2016 07:25:49 +0200
> Cc: Vincent Belaïche <vincent.belaiche@gmail.com>
> 
> This is a very difficult to reproduce crash. It happens quite scarcely,
> but fortunately, knowing its existence I was running under the
> debugger. Please note that it was w/o the -Q option, and my init file is
> quite a few lines ;-).

Thanks.

Unfortunately, backtraces from optimized builds, even those with -Og
switch, are not reliable enough.  So when you know about an existing
problem that is hard to reproduce, please run an unoptimized version
if you can.

Nevertheless, let's see if we can glean anything useful from this
crash.  Please show the output of these GDB commands:

  (gdb) p PT_ADDR
  (gdb) p GPT_ADDR
  (gdb) p GPT