bug#74902: 31.0.50; Segfault when deleting frames

[Eli Zaretskii <eliz@gnu.org>]

> Date: Sun, 15 Dec 2024 14:01:17 -0800
> From:  Steven Allen via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> 
> I use EXWM and, Emacs very occasionally seems to crash when closing
> floating windows. Specifically, it crashes when deleting the frame
> wrapping the floating window. Unfortunately, I don't have a great way to
> reproduce it with a minimal setup or to reproduce it reliably enough to
> grab a trace with GDB.
> 
> As far as I can tell, this is because `delete-frame' calls `delq' (from
> C) which then handles a signal (not sure what signal) via the
> `FOR_EACH_TAIL' macro while deleting the frame. Unfortunately, that
> eventually calls `gobble_input' which operates on frames.
> 
> 
> Backtrace:
> 
>     /usr/bin/emacs(emacs_backtrace+0x4e) [0x61e77935447e]
>     /usr/bin/emacs(terminate_due_to_signal+0xaf) [0x61e7791a4c5d]
>     /usr/bin/emacs(+0x5e062) [0x61e7791a6062]
>     /usr/lib/libc.so.6(+0x42150) [0x7e3a544dc150]
>     /usr/bin/emacs(+0xeff78) [0x61e779237f78]
>     /usr/bin/emacs(+0x19a564) [0x61e7792e2564]
>     /usr/bin/emacs(+0x19a829) [0x61e7792e2829]
>     /usr/bin/emacs(+0x1a1c58) [0x61e7792e9c58]
>     /usr/bin/emacs(+0x1b0bb8) [0x61e7792f8bb8]
>     /usr/bin/emacs(gobble_input+0x272) [0x61e77933f3a2]
>     /usr/bin/emacs(probably_quit+0xc6) [0x61e7793ec666]
>     /usr/bin/emacs(Fdelq+0xb6) [0x61e77940c196]
>     /usr/bin/emacs(delete_frame+0x2d4) [0x61e7791d77b4]
>     /usr/bin/emacs(Fdelete_frame+0x17) [0x61e7791d8a07]

This is less useful than a backtrace could be.  Can you run Emacs
under GDB, and when it crashes, type

  (gdb) thread apply all bt

and post here everything GDB produces as result?