Thanks. Now the chance of the bug becomes very low, but I managed to get
another backtrace. I think we are close to the end.

Thread 1 "emacs" hit Breakpoint 1, signal_or_quit (error_symbol=...,
data=..., keyboard_quit=false) at eval.c:1793
1793 {
#0  signal_or_quit (error_symbol=..., data=..., keyboard_quit=false) at
eval.c:1793
#1  0x0000560d8c635853 in quit () at eval.c:1783
#2  0x0000560d8c635731 in process_quit_flag () at eval.c:1730
#3  0x0000560d8c63577d in maybe_quit () at eval.c:1750
#4  0x0000560d8c64aff7 in internal_equal (o1=..., o2=...,
equal_kind=EQUAL_PLAIN, depth=0, ht=...) at fns.c:2591
#5  0x0000560d8c64a8e6 in Fequal (o1=..., o2=...) at fns.c:2500
#6  0x0000560d8c711c0d in search_image_cache (f=0x560d8d870a78, spec=...,
hash=4330934697943008934, foreground=15457202, background=1908769,
font_size=20, font_family=0x560d8d81e1e8 "DejaVu Sans Mono",
ignore_colors=false) at image.c:1623
#7  0x0000560d8c713b6a in lookup_image (f=0x560d8d870a78, spec=...,
face_id=18) at image.c:2450
#8  0x0000560d8c3e60ea in handle_single_display_spec (it=0x7ffeb78b4820,
spec=..., object=..., overlay=..., position=0x7ffeb78b4970, bufpos=0,
display_replaced=0, frame_window_p=true, enable_eval_p=true) at xdisp.c:5791
#9  0x0000560d8c3e380f in handle_display_spec (it=0x7ffeb78b4820, spec=...,
object=..., overlay=..., position=0x7ffeb78b4970, bufpos=0,
frame_window_p=true) at xdisp.c:5278
#10 0x0000560d8c3e3001 in handle_display_prop (it=0x7ffeb78b4820) at
xdisp.c:5187
#11 0x0000560d8c3df423 in handle_stop (it=0x7ffeb78b4820) at xdisp.c:3854
#12 0x0000560d8c3ee685 in next_element_from_string (it=0x7ffeb78b4820) at
xdisp.c:8524
#13 0x0000560d8c3ebab6 in get_next_display_element (it=0x7ffeb78b4820) at
xdisp.c:7500
#14 0x0000560d8c42f88f in display_string (string=0x0, lisp_string=...,
face_string=..., face_string_pos=0, start=0, it=0x7ffeb78b4820,
field_width=0, precision=11, max_x=300, multibyte=0) at xdisp.c:27323
#15 0x0000560d8c42bd6d in display_mode_element (it=0x7ffeb78b4820, depth=4,
field_width=-23, precision=-23, elt=..., props=..., risky=false) at
xdisp.c:25901
#16 0x0000560d8c42cbe1 in display_mode_element (it=0x7ffeb78b4820, depth=3,
field_width=0, precision=0, elt=..., props=..., risky=false) at
xdisp.c:26149
#17 0x0000560d8c42cbe1 in display_mode_element (it=0x7ffeb78b4820, depth=2,
field_width=0, precision=0, elt=..., props=..., risky=false) at
xdisp.c:26149
#18 0x0000560d8c42c59b in display_mode_element (it=0x7ffeb78b4820, depth=1,
field_width=0, precision=0, elt=..., props=..., risky=false) at
xdisp.c:26072
#19 0x0000560d8c42aab6 in display_mode_line (w=0x560d8e5cf430,
face_id=TAB_LINE_FACE_ID, format=...) at xdisp.c:25585
#20 0x0000560d8c3d3123 in pos_visible_p (w=0x560d8e5cf430, charpos=11524,
x=0x7ffeb78ba904, y=0x7ffeb78ba908, rtop=0x7ffeb78ba948,
rbot=0x7ffeb78ba950, rowh=0x7ffeb78ba90c, vpos=0x7ffeb78ba910) at
xdisp.c:1697
#21 0x0000560d8c40f746 in redisplay_window (window=...,
just_this_one_p=false) at xdisp.c:18882
#22 0x0000560d8c406b37 in redisplay_window_0 (window=...) at xdisp.c:16623
#23 0x0000560d8c634ef8 in internal_condition_case_1 (bfun=0x560d8c406af1
<redisplay_window_0>, arg=..., handlers=..., hfun=0x560d8c406ab5
<redisplay_window_error>) at eval.c:1502
#24 0x0000560d8c406a86 in redisplay_windows (window=...) at xdisp.c:16603
#25 0x0000560d8c406a38 in redisplay_windows (window=...) at xdisp.c:16597
#26 0x0000560d8c4053ba in redisplay_internal () at xdisp.c:16071
#27 0x0000560d8c402d5b in redisplay () at xdisp.c:15287
#28 0x0000560d8c5547ad in read_char (commandflag=1, map=...,
prev_event=..., used_mouse_menu=0x7ffeb78be96d, end_time=0x0) at
keyboard.c:2539
#29 0x0000560d8c5681bf in read_key_sequence (keybuf=0x7ffeb78beb50,
prompt=..., dont_downcase_last=false, can_return_switch_frame=true,
fix_current_buffer=true, prevent_redisplay=false) at keyboard.c:9569
#30 0x0000560d8c5509fe in command_loop_1 () at keyboard.c:1376
#31 0x0000560d8c634e15 in internal_condition_case (bfun=0x560d8c550560
<command_loop_1>, handlers=..., hfun=0x560d8c54f9ac <cmd_error>) at
eval.c:1478
#32 0x0000560d8c550121 in command_loop_2 (handlers=...) at keyboard.c:1117
#33 0x0000560d8c633f0c in internal_catch (tag=..., func=0x560d8c5500f6
<command_loop_2>, arg=...) at eval.c:1198
#34 0x0000560d8c5500c1 in command_loop () at keyboard.c:1095
#35 0x0000560d8c54f457 in recursive_edit_1 () at keyboard.c:720
#36 0x0000560d8c54f673 in Frecursive_edit () at keyboard.c:792
#37 0x0000560d8c54b21f in main (argc=1, argv=0x7ffeb78befd8) at emacs.c:2310
$61 = 11524

Eli Zaretskii <eliz@gnu.org> 于2021年8月18日周三 上午2:31写道：

> > From: Amai Kinono <amaikinono@gmail.com>
> > Date: Wed, 18 Aug 2021 02:09:14 +0800
> > Cc: 44448@debbugs.gnu.org
> >
> > When I press Ctrl+f+g+b, the point jumps back to 11524. Here's the
> backtrace:
> >
> > ```
> > Thread 1 "emacs" hit Breakpoint 1, signal_or_quit (error_symbol=...,
> data=..., keyboard_quit=false) at
> > eval.c:1793
> > 1793 {
> > #0  signal_or_quit (error_symbol=..., data=..., keyboard_quit=false) at
> eval.c:1793
> > #1  0x000056215e7d87ad in quit () at eval.c:1783
> > #2  0x000056215e7d868b in process_quit_flag () at eval.c:1730
> > #3  0x000056215e7d86d7 in maybe_quit () at eval.c:1750
> > #4  0x000056215e7eae6f in Fdelq (elt=..., list=...) at fns.c:1841
> > #5  0x000056215e7fbb95 in font_put_extra (font=..., prop=..., val=...)
> at font.c:745
> > #6  0x000056215e8042a5 in font_clear_prop (attrs=0x7ffd696120e0,
> prop=FONT_SLANT_INDEX) at
> > font.c:3114
> > #7  0x000056215e683b71 in merge_face_vectors (w=0x562161abb2c8,
> f=0x562160c3ca78,
> > from=0x7ffd69611cb0, to=0x7ffd696120e0,
> named_merge_points=0x7ffd69611c90) at xfaces.c:2234
> > #8  0x000056215e6841fb in merge_named_face (w=0x562161abb2c8,
> f=0x562160c3ca78, face_name=...,
> > to=0x7ffd696120e0, named_merge_points=0x7ffd69611c90, attr_filter=0) at
> xfaces.c:2350
> > #9  0x000056215e685b4e in merge_face_ref (w=0x562161abb2c8,
> f=0x562160c3ca78, face_ref=...,
> > to=0x7ffd696120e0, err_msgs=true, named_merge_points=0x0, attr_filter=0)
> at xfaces.c:2834
> > #10 0x000056215e6908b2 in face_at_buffer_position (w=0x562161abb2c8,
> pos=11394,
> > endptr=0x7ffd696121e0, limit=11494, mouse=false, base_face_id=0,
> attr_filter=0) at xfaces.c:6441
> > #11 0x000056215e583e8e in face_at_pos (it=0x7ffd69613900, attr_filter=0)
> at xdisp.c:4379
> > #12 0x000056215e584177 in handle_face_prop (it=0x7ffd69613900) at
> xdisp.c:4475
> > #13 0x000056215e582423 in handle_stop (it=0x7ffd69613900) at xdisp.c:3854
> > #14 0x000056215e592956 in next_element_from_buffer (it=0x7ffd69613900)
> at xdisp.c:8905
> > #15 0x000056215e58ea69 in get_next_display_element (it=0x7ffd69613900)
> at xdisp.c:7494
> > #16 0x000056215e5c590d in display_line (it=0x7ffd69613900,
> cursor_vpos=17) at xdisp.c:23588
> > #17 0x000056215e5b5c7e in try_window (window=..., pos=..., flags=1) at
> xdisp.c:19499
> > #18 0x000056215e5b2859 in redisplay_window (window=...,
> just_this_one_p=false) at xdisp.c:18906
>
> Thanks, I installed another fix for this.
>