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

[Visuwesh]

[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 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

    (gdb) ptype Qnil
    type = struct Lisp_Object {
        Lisp_Word i;
    }