bug#18420: 24.3; interaction with external process hangs emacs

[Eli Zaretskii]

> From: Stephen Leake <stephen_leake@stephe-leake.org>
> Date: Mon, 08 Sep 2014 12:00:42 -0500
> 
> Is there any way to get lisp names from the Ffuncall entries? That would
> be nice.

"xbacktrace" 9defined in src/.gdbinit) should display the Lisp-level
backtrace.  But beware: it calls functions inside Emacs, so it could
hang if Emacs is stuck.

The (tedious) fallback is to do this:

  #12 0x0110521b in Ffuncall (nargs=nargs@entry=1, args=args@entry=0x88ea34)
      at eval.c:2876

  (gdb) p args[0]
  (gdb) xtype # will usually say "Lisp symbol"
  (gdb) xsymbol