bug#22818: 25.1.1 Emacs.app crash ns_compute_glyph_string_overhangs

[Eli Zaretskii]

> Date: Sat, 19 Nov 2016 19:05:39 +0000
> From: Alan Third <alan@idiocy.org>
> Cc: josh@berdine.net, 22818@debbugs.gnu.org
> 
> >   (gdb) break Fredraw_display
> >   (gdb) r -Q
> > 
> > Then, after Emacs starts up, type "M-x redraw-display RET", and at the
> > GDB prompt type:
> > 
> >   (gdb) p lface_id_to_name[17]
> >   (gdb) xsymbol
> > 
> > What does that show?
> > 
> > And what is the value of next_lface_id at that point?
> 
> (gdb) p lface_id_to_name[17]
> $1 = 31008
> (gdb) xsymbol
> $2 = (struct Lisp_Symbol *) 0x7ab8
> Cannot access memory at address 0x7ac0
> (gdb) p next_lface_id
> $3 = 84

Strange.  What about other indices between zero and 83?  Are they all
invalid symbols like this one?