bug#9436: 24.0.50; Segmentation fault during redisplay

[Eli Zaretskii]

> Date: Thu, 25 Sep 2014 15:59:57 +1200
> From: aidalgol@amuri.net
> 
> I think I am running into this bug.  Backtrace attached.

I don't think we can trust any crash backtraces from the 64-bit
Cygwin-w32 builds until we understand what happens with the assertion
violations in bidi.c.

Let's try anyway (assuming you still have this in a debugger):

> #0  0x0000000100650249 in composition_update_it (cmp_it=0x226a98, 
> charpos=1819, bytepos=1819, string=4306700338) at composite.c:1322
>         cmp = 0x226240
>         i = 0
>         c = 2272050

Please show what these commands print in GDB:

 (gdb) frame 0
 (gdb) p *cmp
 (gdb) frame 1
 (gdb) p it->cmp
 (gdb) p it->current

And I imagine that your buffer was pure-ASCII (is that right?), so no
compositions are involved and we probably shouldn't be even entering
composition_update_it at all.