bug#22120: 25.1.50; segfault while running circe

[Eli Zaretskii <eliz@gnu.org>]

> From: Eric Hanchrow <eric.hanchrow@gmail.com>
> Date: Tue, 8 Dec 2015 12:36:52 -0800
> Cc: 22120@debbugs.gnu.org
> 
> Dunno if I'm doing this right:

You are, thanks.

> (gdb) down
> #1  CAR (c=...) at lisp.h:1244
> 1244      return (CONSP (c) ? XCAR (c)
> (gdb)
> #0  XCAR (c=...) at lisp.h:1216
> 1216      return lisp_h_XCAR (c);
> (gdb) p c
> $4 = <optimized out>
> (gdb) up
> #1  CAR (c=...) at lisp.h:1244
> 1244      return (CONSP (c) ? XCAR (c)
> (gdb) p c
> $5 = <optimized out>
> (gdb) up
> #2  Fcar (list=...) at data.c:527
> 527       return CAR (list);
> (gdb) p list
> $6 = {
>   i = 7791354264813860195
> }
> (gdb) xpr list
> Lisp_Cons
> $7 = (struct Lisp_Cons *) 0x6c20736c69747560
> Cannot access memory at address 0x6c20736c69747560

That "address" is part of a string: "`utils l" (without the quotes).
So I'm guessing some code is overwriting the stack or writing beyond
the limits of a char array.  The question is where?