bug#47244: 28.0.50; SIGSEGV in long-runnning Emacs

[Eli Zaretskii]

> From: Michael Welsh Duggan <mwd@cert.org>
> Date: Thu, 08 Apr 2021 10:35:53 -0400
> Cc: Michael Welsh Duggan <mwd@md5i.com>,
>  "schwab@linux-m68k.org" <schwab@linux-m68k.org>,
>  "47244@debbugs.gnu.org" <47244@debbugs.gnu.org>
> 
> I've yet to run this code yet (will do so shortly), but I'd like to
> mention that some other debugging I've been doing involving tricky
> breakpoint commands is implying that, somehow, list_windows() is getting
> called while list_windows() is still running.  I've got a breakpoint
> at the beginning of the if clause in window_list() and one at the end,
> and it looks like I'm seeing the first one get called twice without the
> second getting called inbetween.

That could mean some code signals an error, or throws to catchpoint,
before the second breakpoint is hit.