Re: Crashes on draw_glyphs

[Chong Yidong <cyd@stupidchicken.com>]

"Juanma Barranquero" <lekktu@gmail.com> writes:

> The underling bug that causes #872/#1179 is really getting annoying.
>
> Apparently I'm the only one suffering it (perhaps I'm the only one
> compiling Emacs on Windows with GCC 4.3.0), and I've been
> unsuccessfully trying to debug it for weeks. Unfortunately, as soon as
> I even add an assertion, the crash point moves. It seems like the
> thing to do is to run draw_glyphs step-by-step, but with the macros
> and all that it is quite difficult, not to mention that I know very
> little about the redisplay code and that the bug is much harder to
> catch when I compile a non-optimized build.
>
> The breaking point (for my patience, at least) is that I now can crash
> Emacs even without setting unibyte-display-via-language-environment,
> just by doing
>
>   emacs -Q
>   M-x ucs-insert AEGEAN CHECK MARK <return>
>
> which causes an assertion failure.
>
> Breakpoint 1, w32_abort () at w32fns.c:7279
> 7279      button = MessageBox (NULL,
> (gdb) bt
> #0  w32_abort () at w32fns.c:7279
> #1  0x01034045 in fill_glyph_string (s=0x82e8c0, face_id=1,
> start=-1151, end=1, overlaps=0) at xdisp.c:19695
> #2  0x01057492 in draw_glyphs (w=0x2e44a00, x=17, row=0x2ffb260,
> area=TEXT_AREA, start=0, end=1, hl=DRAW_NORMAL_TEXT,
>     overlaps=0) at xdisp.c:20329

Any luck debugging this?

I notice that the START argument in fill_glyph_string is
negative---could you try to trace this back to see where it comes from?