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switching font backends in .emacs.desktop causes crash
From: |
Robert Pluim |
Subject: |
switching font backends in .emacs.desktop causes crash |
Date: |
Fri, 08 Feb 2019 13:09:22 +0100 |
Playing around with the various X font backend build options resulted
in me having a .emacs.desktop like so:
;; -*- mode: emacs-lisp; lexical-binding:t; coding: utf-8-emacs; -*-
;; --------------------------------------------------------------------------
;; Desktop File for Emacs
;; --------------------------------------------------------------------------
;; Created Fri Feb 8 09:02:42 2019
;; Desktop file format version 208
;; Emacs version 27.0.50
;; Global section:
(setq desktop-saved-frameset [frameset 1 (23645 14242 497425
32000) (desktop . "208") "address@hidden" nil
nil ((((minibuffer . t) (undecorated) (override-redirect) (font-backend x))))])
and .emacs:
(custom-set-variables
;; custom-set-variables was added by Custom.
;; If you edit it by hand, you could mess it up, so be careful.
;; Your init file should contain only one such instance.
;; If there is more than one, they won't work right.
'(desktop-save-mode t)
)
I rebuilt with the XFT and X backends (default configuration), and
got:
$ ./emacs
Fatal error 11: Segmentation fault
Backtrace:
./emacs(+0x1338ce)[0x5568bfc208ce]
./emacs(+0x119e4a)[0x5568bfc06e4a]
./emacs(+0x131c9e)[0x5568bfc1ec9e]
./emacs(+0x131f48)[0x5568bfc1ef48]
./emacs(+0x131fcc)[0x5568bfc1efcc]
/lib/x86_64-linux-gnu/libpthread.so.0(+0x12890)[0x7ff5f243f890]
/usr/lib/x86_64-linux-gnu/libXft.so.2(XftCharIndex+0xd)[0x7ff5f5c5568d]
Poking around with gdb, I see that the xftfont field of xftfont_info
is NULL, so I set a watchpoint:
$ gdb emacs
(gdb) l xftfont.c:320
315 ASET (font_object, FONT_FILE_INDEX, filename);
316 font = XFONT_OBJECT (font_object);
317 font->pixel_size = size;
318 font->driver = &xftfont_driver;
319 font->encoding_charset = font->repertory_charset = -1;
320
321 xftfont_info = (struct font_info *) font;
322 xftfont_info->display = display;
323 xftfont_info->xftfont = xftfont;
324 xftfont_info->x_display_id = FRAME_DISPLAY_INFO (f)->x_id;
(gdb) b 324
Breakpoint 3 at 0x204b47: file xftfont.c, line 324.
(gdb) r
Starting program: /home/rpluim/repos/emacs-real-master/src/emacs
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffe4a29700 (LWP 12037)]
[New Thread 0x7fffdf41b700 (LWP 12039)]
[New Thread 0x7fffdea0d700 (LWP 12040)]
Thread 1 "emacs" hit Breakpoint 3, xftfont_open (f=0x55555646b2a0,
entity=XIL(0x5555560a6975), pixel_size=27) at xftfont.c:324
324 xftfont_info->x_display_id = FRAME_DISPLAY_INFO (f)->x_id;
(gdb) watch -l xftfont_info->xftfont
Hardware watchpoint 4: -location xftfont_info->xftfont
(gdb) d 3
(gdb) c
Continuing.
Thread 1 "emacs" hit Hardware watchpoint 4: -location xftfont_info->xftfont
Old value = (XftFont *) 0x5555564738e0
New value = (XftFont *) 0x0
xftfont_close (font=0x5555560a6a60) at xftfont.c:464
464 }
(gdb) bt
#0 0x000055555575914e in xftfont_close (font=0x5555560a6a60) at
xftfont.c:464
#1 0x00005555556fd454 in font_clear_cache (cache=XIL(0x555555e4c8b3),
address@hidden <xftfont_driver>, f=0x55555646b2a0) at font.c:2643
#2 0x0000555555702e35 in font_finish_cache (driver=0x5555559e11e0
<xftfont_driver>, f=0x55555646b2a0) at font.c:2588
#3 0x0000555555702e35 in font_update_drivers (address@hidden,
address@hidden(0x555558155c13)) at font.c:3545
#4 0x00005555555a2a0f in x_set_font_backend (f=0x55555646b2a0,
new_value=<optimized out>, old_value=XIL(0x555555e4c7b3)) at frame.c:4400
#5 0x00005555555a1408 in x_set_frame_parameters (address@hidden,
address@hidden(0x55555815b603)) at frame.c:3933
#6 0x00005555555a1e9c in Fmodify_frame_parameters (frame=<optimized out>,
alist=XIL(0x55555815b603)) at frame.c:3197
Lisp Backtrace:
"modify-frame-parameters" (0xffffb898)
"frameset--restore-frame" (0xffffbc90)
"frameset-restore" (0xffffc1f0)
"desktop-restore-frameset" (0xffffc458)
"desktop-read" (0xffffc7e0)
0x563cec70 PVEC_COMPILED
"run-hooks" (0xffffcae0)
"command-line" (0xffffd388)
"normal-top-level" (0xffffd700)
So it looks like we're closing the xft font backend, because of the
(font-backend x) in the desktop file, and flushing the font cache. Looking at
where it crashes exactly:
(gdb) c
Continuing.
Thread 1 "emacs" received signal SIGSEGV, Segmentation fault.
0x00007ffff446468d in XftCharIndex () from
/usr/lib/x86_64-linux-gnu/libXft.so.2
(gdb) bt
#0 0x00007ffff446468d in XftCharIndex () at
/usr/lib/x86_64-linux-gnu/libXft.so.2
#1 0x0000555555758689 in xftfont_encode_char (font=<optimized out>,
c=<optimized out>)
at xftfont.c:532
#2 0x00005555555d60a9 in get_char_glyph_code (char2b=<synthetic pointer>,
font=0x555557b49470, c=<optimized out>) at xdisp.c:25915
#3 0x00005555555d60a9 in x_produce_glyphs (it=0x7fffffff9b00) at
xdisp.c:28294
Here we're using xftfont_encode_char, even though we've just closed
the XFT font backend and should be using the X one for the minibuffer?
Is the 'it' there caching XFT information?
I have no idea how to fix this. I can reproduce at will if more gdb
info is needed (BTW, emacs-26 has the same issue).
Lisp Backtrace:
"message" (0xffffc458)
"desktop-read" (0xffffc7e0)
0x563cec70 PVEC_COMPILED
"run-hooks" (0xffffcae0)
"command-line" (0xffffd388)
"normal-top-level" (0xffffd700)
- switching font backends in .emacs.desktop causes crash,
Robert Pluim <=