bug#63283: Emacs crash within fontset

[Eli Zaretskii <eliz@gnu.org>]

> Date: Thu, 04 May 2023 19:04:48 +0000
> From:  Seppo Ronkainen via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> run Emacs without configuration and after one second increase the font size a few times
> #+begin_src sh
>   PATH="/home/user/.local/emacs-29.0.90_minimal/inst/bin:${PATH}" gdb --ex run --args emacs -Q ~/examplefilewithunicodetext --eval "(run-at-time 1 '() (lambda() (dotimes (i 10) (text-scale-adjust 1))))"
> #+end_src
> 
> expected behavior: emacs resizes the font
> 
> observed behavior: gdb reports emacs defect in fontset.c on line 555
> src/fontset.c:549
> #+begin_src c
> /* 549 */ static Lisp_Object
> /* 550 */ fontset_find_font (Lisp_Object fontset, int c, struct face /* *fa */ce,
> /* 551 */                    int charset_id, bool fallback)
> /* 552 */ {
> /* 553 */   Lisp_Object vec, font_group;
> /* 554 */   int i, charset_matched = 0, found_index;
> /* 555 */   struct frame *f = (FRAMEP (FONTSET_FRAME (fontset))
> /* 556 */                      ? XFRAME (FONTSET_FRAME (fontset))
> /* 557 */                      : XFRAME (selected_frame));
> #+end_src
> 
> #+begin_export
> 0x00000055557864c8 in fontset_find_font (fontset=fontset@entry=0x20, c=c@entry=12302, face=face@entry=0x5556519100, 
>     charset_id=charset_id@entry=-1, fallback=fallback@entry=false) at fontset.c:555
> 555       struct frame *f = (FRAMEP (FONTSET_FRAME (fontset))
> #+end_export

What do you mean by "gdb reports emacs defect"?  Please show the
complete GDB session, including everything that GDB shows on screen.

Also please send the data about your Emacs and system configuration,
as collected by "M-x report-emacs-bug RET".

Thanks.