bug#66589: 30.0.50; core dump in redisplay

[Eli Zaretskii <eliz@gnu.org>]

> From: Evgeny Zajcev <lg.zevlg@gmail.com>
> Date: Tue, 17 Oct 2023 18:11:43 +0300
> Cc: 66589@debbugs.gnu.org
> 
> (gdb) frame 18
> #18 produce_glyphless_glyph (it=0x7ffef46c5660,
> for_no_font=for_no_font@entry=false, acronym=acronym@entry=0x0) at
> xdisp.c:32165
> 32165             sprintf (buf, "%0*X", it->c < 0x10000 ? 4 : 6, it->c +
> 0u);
> (gdb) p/x it->c
> $2 = 0xfffc71a2
> (gdb) p/x it->char_to_display
> $3 = 0xa
> (gdb) p it->method
> $4 = GET_FROM_BUFFER
> (gdb) pgrowx it->glyph_row
> Undefined command: "pgrowx".  Try "help".
> (gdb) source src/.gdbinit
> Warning: /home/lg/dev/emacs-30/../lwlib: No such file or directory.
> SIGINT is used by the debugger.
> Are you sure you want to change it? (y or n) [answered Y; input not from
> terminal]
> DISPLAY = :0
> TERM = screen-256color
> Breakpoint 1 at 0x55ccdf18ac6a: file emacs.c, line 446.
> Breakpoint 2 at 0x55ccdf27ad60: file xterm.c, line 26945.
> (gdb) pgrowx it->glyph_row
> Cannot access memory at address 0x2c
> (gdb)

OK, thanks.  One more request:

  (gdb) frame 19
  (gdb) p it->current
  (gdb) p current_buffer->zv
  (gdb) p current_buffer->text->beg[10000]@106