bug#69431: 30.0.50; Strange fontificaion behavior

[Eli Zaretskii <eliz@gnu.org>]

> From: Björn Bidar <bjorn.bidar@thaodan.de>
> Cc: acorallo@gnu.org,  yantar92@posteo.net,  monnier@iro.umontreal.ca,
>   69431@debbugs.gnu.org,  hirofumi@mail.parknet.co.jp
> Date: Sun, 07 Apr 2024 18:00:26 +0300
> 
> >> Is there already a bug for this issue or should I open a new one?
> 
> > It depends, I think.  What is the recipe for what you see?
> 
> I can only trigger the bug when I load enough packages to trigger the bug
> First I thought the bug is triggered when I modus themes but it also
> happens without, I just have to load enough packages.
> 
> 
> I attach my init.el (with private information removed) and
> the logs I had from  earlier and now.

It is some kind of recursive call:

  face-attribute->face-attribute-merged-with->face_attribute->...

Looks like a separate problem to me.  It is important to understand
what face causes this, and what is that face's spec.

Also, please make a point of loading the src/.gdbinit file from the
Emacs source tree before running Emacs under GDB, so that the
backtrace includes also the Lisp backtrace, and shows Lisp objects in
human-readable format, for easier reading.

> I tried to find which package exactly triggers the bug but I did not
> manage to do that. I only know that it is triggered through the use of
> faces.

Both backtraces are almost identical, and in both the problem seems to
be triggered by loading and enabling a theme.  So I don't think I
understand what you say here about "enough packages" -- I don't
suppose all of the packages you load are themes, are they?  IOW, can
you show a backtrace from a crash that is not caused by loading a
theme?  E.g., what happens if you remove all theme loading and related
stuff from your init files?