bug#5609: 23.1.92; segfault in composition_compute_stop_pos

[Kenichi Handa]

In article <87r5oed905.fsf@stupidchicken.com>, Chong Yidong 
<cyd@stupidchicken.com> writes:

> Hi Handa-san,
> It looks like your changes to composite.c last month may have led to a
> bug.  Could you take a look?  Thanks!

Ok, I'll work on it.

---
Kenichi Handa
handa@m17n.org

> Sven Joachim <svenjoac@gmx.de> wrote:

> > During the last weeks I experienced several segfaults, mostly in Dired,
> > but unfortunately I did not run Emacs under GDB.  This time I did.
> > I visited a file named "Makefile" and started an I-search for
> > "distcheck" when Emacs segfaulted.  This is not reproducible.

> > (gdb) xbacktrace
> > (gdb) bt full
> > #0 0x081e30b4 in composition_compute_stop_pos (cmp_it=0xffffb040,
> >     charpos=16, bytepos=26,
> >     endpos=17, string=<value optimized out>) at composite.c:1072
> >         elt = <value optimized out>
> >         start = 0
> >         end = -22168
> >         c = 14719988
> >         prop = 0
> >         val = <value optimized out>
> > #1 0x08079548 in reseat_to_string (it=<value optimized out>, s=0x0,
> >     string=<value optimized out>,
> >     charpos=0, precision=-8, field_width=17, multibyte=1) at xdisp.c:5613
> > No locals.
> >
> > #2  0x08080031 in display_string (string=0x83ec9f2 "",
> >     lisp_string=154714081, face_string=<value optimized out>,
> >     face_string_pos=1, start=0, it=0xffffac88, field_width=17,
> >     precision=-8, max_x=0, multibyte=1) at xdisp.c:18866
> >         hpos_at_start = 8
> >         saved_face_id = 1
> >         row = 0x8f77368