bug#73752: 29.4; Ligatures are randomly rendered with extra spaces

[Eli Zaretskii]

> From: Visuwesh <visuweshm@gmail.com>
> Cc: dev@real-or-random.org,  xuan@xlk.me,  73752@debbugs.gnu.org
> Date: Sat, 02 Nov 2024 23:01:37 +0530
> 
> [சனி நவம்பர் 02, 2024] Eli Zaretskii wrote:
> 
> >> From: Visuwesh <visuweshm@gmail.com>
> >> Cc: dev@real-or-random.org,  xuan@xlk.me,  73752@debbugs.gnu.org
> >> Date: Sat, 02 Nov 2024 22:34:44 +0530
> >> 
> >> [சனி நவம்பர் 02, 2024] Eli Zaretskii wrote:
> >> 
> >> > Thanks, but this is a false alarm: the lgstring's glyphs don't have
> >> > the [XOFF YOFF WADJUST] component.  So either my breakpoint condition
> >> > is somehow wrong, or you mistyped it, or something else.
> >> 
> >> I don't think I mistyped the condition at least.  Here's what I typed:
> >> 
> >>     (gdb) break hbfont.c:598 if xoff == 0 && yoff == 0 && wadjust ==
> >> metrics.width && LGLYPH_ADJUSTMENT(lglyph) != Qnil
> >> 
> >> >  What does GDB show if you type
> >> >
> >> >   (gdb) p LGLYPH_ADJUSTMENT(lglyph)
> >> >   (gdb) p Qnil
> >> 
> >>     (gdb) p LGLYPH_ADJUSTMENT(lglyph)
> >>     $3 = XIL(0)
> >>     (gdb) p Qnil
> >>     $4 = XIL(0)
> >
> > OK, but then why did the breakpoint break, when the condition is
> > obviously false: LGLYPH_ADJUSTMENT(lglyph) == Qnil.
> >
> > What happens if you type this:
> >
> >   (gdb) p Qnil+0
> 
>     (gdb) p Qnil+0
>     Attempt to take address of value not located in memory.

And this:

  (gdb) ptype Qnil