From: Eli Zaretskii <eliz@gnu.org>
To: Ken Raeburn <raeburn@permabit.com>
Cc: 18162@debbugs.gnu.org
Subject: bug#18162: 24.3.92; segfault on null face pointer in face_for_char
Date: Sun, 03 Aug 2014 18:04:29 +0300 [thread overview]
Message-ID: <83bns1r4w2.fsf@gnu.org> (raw)
In-Reply-To: <CFCB082F-B750-4479-9399-C83D00FAB9A6@permabit.com>
> From: Ken Raeburn <raeburn@permabit.com>
> Date: Sun, 3 Aug 2014 02:51:38 -0400
> Cc: 18162@debbugs.gnu.org
>
> On Aug 2, 2014, at 08:50, Eli Zaretskii <eliz@gnu.org> wrote:
> > Moreover, even if I force the call to clear_font_cache by invoking
> > clear-font-cache in the progn, I don't see a crash, and the use count
> > of the frame's face cache is not zero.
> >
> > So one way of tracking this down would be to put a breakpoint in
> > Fclear_face_cache, and when it breaks, step through the function until
> > it assigns the frame pointer to 'f', and put a watchpoint on
> > f->face_cache->used, to see which code zeroes it. My guess would be
> > that some code calls free_realized_faces (I misremembered earlier:
> > clear_face_cache doesn't do that).
>
> In the code I'm looking at, clear_face_cache can call free_all_realized_faces, but only if FRAME_DISPLAY_INFO(f)->n_fonts is larger than 10 for some frame.
Yes, I meant clear_face_cache doesn't do that directly. And since
free_realized_faces is called from several other places, it's best not
to assume this particular call is necessarily the culprit.
> (And either clear_fonts_p is set, or you've made over 500 calls since the last font cache cleaning.) In my first evaluation of the lisp code I gave, the n_fonts field had the value 7; on the second evaluation it had the value 12, the cache got cleared, the null pointer was stored, and Emacs segfaulted.
>
> I've done next to nothing with fonts and faces in Emacs source code, so I'm not sure what a good way is to drive up the number. If I run my test again without list-faces-display, the font counts I'm seeing are first 4 and then 7 for repeated evaluations, as displayed via gdb breakpoint commands. If I split the window with C-x 2 then the count goes up to 8 (new inactive mode line?). Reducing the font size (C-x -) made it jump to 14, and 15 on repeated evaluations, without triggering the problem, but when I set the font size back (C-x +) and evaluated the expression one more time, I got the crash.
Does the patch below help?
=== modified file 'src/fontset.c'
--- src/fontset.c 2014-01-01 07:43:34 +0000
+++ src/fontset.c 2014-08-03 15:00:11 +0000
@@ -1860,6 +1860,8 @@ DEFUN ("internal-char-font", Finternal_c
return Qnil;
if (!FRAME_WINDOW_P (f))
return Qnil;
+ if (FRAME_FACE_CACHE (f)->used == 0)
+ recompute_basic_faces (f);
face_id = FACE_FOR_CHAR (f, FACE_FROM_ID (f, face_id), c, pos, Qnil);
face = FACE_FROM_ID (f, face_id);
if (face->font)
next prev parent reply other threads:[~2014-08-03 15:04 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-07-31 23:24 bug#18162: 24.3.92; segfault on null face pointer in face_for_char Ken Raeburn
2014-08-01 5:57 ` Eli Zaretskii
2014-08-01 8:46 ` Ken Raeburn
2014-08-02 1:52 ` Ken Raeburn
2014-08-02 6:49 ` Eli Zaretskii
2014-08-02 10:00 ` Ken Raeburn
2014-08-02 10:41 ` Eli Zaretskii
2014-08-02 12:50 ` Eli Zaretskii
2014-08-03 6:51 ` Ken Raeburn
2014-08-03 15:04 ` Eli Zaretskii [this message]
2014-08-07 4:12 ` Ken Raeburn
2014-08-07 15:19 ` Eli Zaretskii
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