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bug#23386: Segfault when messing with font-backend
From: |
Stefan Monnier |
Subject: |
bug#23386: Segfault when messing with font-backend |
Date: |
Wed, 27 Apr 2016 10:23:00 -0400 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) |
>> % emacs -Q --eval "(push '(font-backend x) default-frame-alist)"
>> I get a segfault. This is with the latest emacs-25.
> Not reproducible here, but then I cannot run an X version. (I did try
> an equivalent for Windows; it didn't crash.)
Not surprised: it seems specific to the X11 code.
>> Program received signal SIGSEGV, Segmentation fault.
>> 0xf70b3b36 in XftCharIndex () from /usr/lib/i386-linux-gnu/libXft.so.2
>> (gdb) xbacktrace
>> (gdb) bt
>> #0 0xf70b3b36 in XftCharIndex () from /usr/lib/i386-linux-gnu/libXft.so.2
>> #1 0x082d4d69 in xftfont_encode_char (font=0x8779b00, c=92) at xftfont.c:537
> Can you tell which arguments to XftCharIndex were invalid in this
> case?
I guess it's the second arg (xftfont_info->xftfont), which is NULL.
Program received signal SIGSEGV, Segmentation fault.
0xf70b3b36 in XftCharIndex () from /usr/lib/i386-linux-gnu/libXft.so.2
(gdb) up
#1 0x082d4d69 in xftfont_encode_char (font=0x8779af0, c=92) at
xftfont.c:537
(gdb) p xftfont_info->display
$1 = (Display *) 0x86f2368
(gdb) p xftfont_info->xftfont
$2 = (XftFont *) 0x0
(gdb) p c
$3 = 92
(gdb)
> Also, is 'x' a valid font-backend symbol?
AFAIK yes.
> It's strange that Emacs uses xftfont when it should have been using
> xfont instead (AFAIU).
Indeed, that seems to be a big part of the problem.
Stefan