bug#50571: 28.0.50; Redisplay segfaults with empty face cache

[Basil L. Contovounesios]

Eli Zaretskii [2021-09-14 16:33 +0300] wrote:

>> Date: Tue, 14 Sep 2021 16:03:02 +0300
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: 50571@debbugs.gnu.org
>> 
>> Thanks, I see the reason now.  It's because we allow to have arbitrary
>> Lisp to be registered in jit-lock-functions, and then that arbitrary
>> Lisp is called in the middle of redisplay, and in this case creates a
>> whole new frame with faces.  As luck would have it, we decide right
>> there and then perform routine maintenance and release all the faces
>> on all the frames...
>> 
>> I'm thinking about the best solution for this.
>
> Does the patch below give good results?

Yes, applying it makes the issue go away, and reverting it reintroduces
the segfault.  I didn't notice any other issues.  Thanks!

-- 
Basil