bug#71243: 30.0.50; SIGSEGV: realize_face tries to uncache a null face

[Daniel Clemente]

I can't reproduce this, and the fix looks fine, so I guess it can be closed. Thanks.

On Tue, 28 May 2024 at 16:05, Eli Zaretskii <eliz@gnu.org> wrote:

> From: Daniel Clemente <n142857@gmail.com>
> Date: Tue, 28 May 2024 15:33:24 +0000
>
> This is similar to bug#71224. I was opening+killing frames in a loop with:
>
> for j in `seq 350`; do for i in `seq 10`; do urxvt -e emacsclient '-nw' '-e' '(dired "~")' &; done; sleep 2 && killall
> emacsclient; done
>
> It's not too much stress, it's just opening 10 frames, waiting 2 seconds, closing them, and repeating. It takes
> time (and luck) until it reaches this SIGSEGV, it took around 5 minutes and several previous attempts where I
> saw a different issue (bug#71223).
> I can't reliably reproduce this.
>
> The emacs daemon was using this ~/.emacs. It's something I was using when reproducing bug#71176
> (already fixed, though maybe some call to realize_face needs to be protected here to avoid this new case). I'm
> not sure if the crash would happen with an empty emacs.
>
> (setq garbage-collection-messages t)
> (set-face-foreground 'default "#bbb")
>
> Built without X support, running on X. My build is in a recent commit and with no patches added.
>
> Note that the stack is 12k functions high. Usually when this happens there will be a stack overflow (see
> bug#71223) and Emacs reacts weirdly. I didn't see the stack overflow message this time, but the SIGSEGV
> may be related to being at the stack limit.
> In that case there may be nothing important to fix and this can be closed.
>
> process server <2814> no longer connected to pipe; closed it
> process server <2815> no longer connected to pipe; closed it
> process server <2822> no longer connected to pipe; closed it
> process server <2823> no longer connected to pipe; closed it
> process server <2824> no longer connected to pipe; closed it
> process server <2825> no longer connected to pipe; closed it
> process server <2832> no longer connected to pipe; closed it
> process server <2833> no longer connected to pipe; closed it
> process server <2834> no longer connected to pipe; closed it
> process server <2835> no longer connected to pipe; closed it
>
> Program received signal SIGSEGV, Segmentation fault.
> 0x00005555556664cc in uncache_face (c=0x555557a04a40, face=0x0) at xfaces.c:4929
> 4929  int i = face->hash % FACE_CACHE_BUCKETS_SIZE;
> (gdb) bt
> #0  0x00005555556664cc in uncache_face (c=0x555557a04a40, face=0x0) at xfaces.c:4929
> #1  0x0000555555668663 in realize_face (cache=0x555557a04a40, attrs=0x7fffffba6500,
> former_face_id=13) at xfaces.c:6060
> #2  0x0000555555668608 in realize_named_face (f=0x555557c5a558, symbol=XIL(0x117f0), id=13) at
> xfaces.c:6037

Thanks, I installed a fix.