bug#33885: 27.0.50; PUA character makes emacs crash

[Eli Zaretskii]

> Date: Fri, 28 Dec 2018 13:38:56 +0100 (CET)
> Cc: 33885@debbugs.gnu.org
> From: Werner LEMBERG <wl@gnu.org>
> 
> >   break x_produce_glyphs if it->char_to_display == 0xe6a3
> 
> OK, did that.  Here's the contents of `it' ($11), `face' ($12), and
> `font' ($13), respectively, at xdisp.c:28221.  The `font' entry looks
> very strange.

Agreed, it looks like descent has the wrong sign.

> AFAICS, it's not a problem related to a single glyph.  We rather have
> to check how the `Cardo' fonts get loaded into Emacs; it looks as if
> the global font descent value is incorrect.  Please tell me (a) how to
> identify the font used for U+E6A3, and (b) where to set a breakpoint
> to see the font loading in action.

(a) font->props[2] names the font, so:

  (gdb) pp font->props[2]

should display its name in human-readable form.  To have the "pp"
command in GDB, you need to issue the command

  (gdb) source /path/to/emacs/src/.gdbinit

before you type the above.

(b) Given your list of features, which includes XFT, I think you want
to set a breakpoint in xftfont_open, where there's a call to
XftFontOpenPattern.

Thanks.