bug#58334: 29.0.50; ASAN heap use after free in gui_produce_glyphs

[Eli Zaretskii]

> From: Po Lu <luangruo@yahoo.com>
> Cc: Eli Zaretskii <eliz@gnu.org>,  58334@debbugs.gnu.org
> Date: Fri, 07 Oct 2022 16:36:05 +0800
> 
> Gerd Möllmann <gerd.moellmann@gmail.com> writes:
> 
> > And, while vaccuming, I also wondered what happens with the glyph
> > matrices, and maybe other global state?
> 
> Isn't input blocked wherever the glyph matrices are modified?

No, not in general.  Why would it?  We don't allow re-entering
redisplay anyway.

> If not, how come expose_frame always works correctly?

expose_frame doesn't modify glyph matrices, it only uses them,
i.e. accesses them in read-only fashion.  At least AFAIK, that is.