bug#72692: Emacs 31.05 (40eecd594ac) get SIGSEGV on Linux (Linux 6.6.45 Kde Wayland)

[Eli Zaretskii <eliz@gnu.org>]

> Cc: execvy@gmail.com, 72692@debbugs.gnu.org
> Date: Mon, 19 Aug 2024 19:49:03 +0300
> From: Eli Zaretskii <eliz@gnu.org>
> 
> > Date: Mon, 19 Aug 2024 16:34:59 +0000
> > From: Pip Cet <pipcet@protonmail.com>
> > Cc: execvy@gmail.com, 72692@debbugs.gnu.org
> > 
> > "Eli Zaretskii" <eliz@gnu.org> writes:
> > 
> > > Thanks, but I'd also like to see the callers which call
> > > free_realized_face in a way that causes the latter to call
> > > free_face_fontset.  That's why I asked for backtraces from those
> > > calls, but I don't think you sent such backtraces.  What you sent was
> > 
> > Just for the record, you asked:
> > 
> > > So can you show a backtrace from the call to free_realized_faces
> > > (supposedly called by realize_basic_faces?) which causes these
> > > printfs:
> > > > fontset 103 used for face 0x117cca0
> > > > fontset 103 used for face 0x2a7a3c0
> > > > fontset 103 used for face 0x117cca0
> > > > fontset 103 used for face 0x2a62860
> > 
> > ... which I misunderstood.  Sorry.
> 
> Sorry for being unclear.
> 
> > Is this what you want?
> 
> Yes, recompute_basic_faces was the prime suspect.  I think we added
> several calls to it over the last years, to fix problems with face
> cache being emptied at some unexpected times.
> 
> > Indeed, I can report that the bug doesn't seem to occur after this
> > simple change:
> > 
> > diff --git a/src/xfaces.c b/src/xfaces.c
> > index 684b6ccfac7..a4ac9c0787a 100644
> > --- a/src/xfaces.c
> > +++ b/src/xfaces.c
> > @@ -736,6 +736,7 @@ recompute_basic_faces (struct frame *f)
> >        clear_face_cache (false);
> >        if (!realize_basic_faces (f))
> >         emacs_abort ();
> > +      f->face_change = true;
> >      }
> >  }
> >  
> > 
> > So something like that (though moving the call down into
> > realize_basic_faces or even further would be good) would probably work
> > for the OP, and emacs-30?
> 
> I think setting the flag in recompute_basic_faces should be enough.
> Let me think about it some more.

I decided to go with this change only, and installed it on the
emacs-30 release branch.  Let's hope it makes this tricky problem go
away.

I'm closing this bug.  If the problem resurfaces, we can reopen it.