bug#63988: 30.0.50; Recent header line format changes cause spin/seg fault with format-mode-line

[Aaron Jensen]

On Thu, Jun 15, 2023 at 1:58 AM Eli Zaretskii <eliz@gnu.org> wrote:
>
> > From: Eshel Yaron <me@eshelyaron.com>
> > Cc: aaronjensen@gmail.com,  63988@debbugs.gnu.org,  Stefan Monnier
> >  <monnier@iro.umontreal.ca>
> > Date: Sat, 10 Jun 2023 12:07:22 +0300
> >
> > > So maybe we should declare this feature a failed experiment and remove
> > > it?
> >
> > FWIW I think that make sense, but IMO it'd be best to only remove the
> > treatment of `:eval` in `window_wants_header_line`, and keep the new
> > treatment of `header-line-format` being a cons cell with a void or
> > nil-valued variable car.  That's still useful because it works well with
> > minor mode variables, and it's less risky as it doesn't involve
> > evaluating arbitrary lisp, just inspecting a variable.
>
> Why would it make sense to leave the non-nil car case?
>
> It sounds like the consensus here is that indeed this feature is not
> worth the complications, and so, unless I hear some good reasons not
> to do so, I intend to delete it in a week's time.

I strongly support this. It's a major performance regression for me
and it seems to correspond with crashes on window resizing:

Thread 0 Crashed::  Dispatch queue: com.apple.main-thread
0   libsystem_kernel.dylib               0x191054724 __pthread_kill + 8
1   libsystem_pthread.dylib               0x19108bc28 pthread_kill + 288
2   libsystem_c.dylib                     0x190f6246c raise + 32
3   Emacs                                 0x100a215b0
terminate_due_to_signal + 212
4   Emacs                                 0x100a21dfc emacs_abort + 20
5   Emacs                                 0x1009f0594 ns_term_shutdown + 132
6   Emacs                                 0x1008dcc90 shut_down_emacs + 332
7   Emacs                                 0x100a21578
terminate_due_to_signal + 156
8   Emacs                                 0x1008fd4bc
deliver_fatal_thread_signal + 128
9   Emacs                                 0x1008fee80 handle_sigsegv + 64
10  libsystem_platform.dylib             0x1910baa24 _sigtramp + 56
11  Emacs                                 0x10083a90c start_display + 56
12  Emacs                                 0x10085010c try_window + 144
13  Emacs                                 0x10086c88c display_echo_area_1 + 136
14  Emacs                                 0x1008496dc
with_echo_area_buffer + 784
15  Emacs                                 0x1008485bc echo_area_display + 268
16  Emacs                                 0x1008483bc message3_nolog + 548
17  Emacs                                 0x100847f5c message3 + 132
18  Emacs                                 0x100952470 Fmessage + 68
19  Emacs                                 0x100958074 eval_sub + 1980
20  Emacs                                 0x10095824c Fprogn + 48
21  Emacs                                 0x10095d728 funcall_lambda + 1276
22  Emacs                                 0x10095c284 apply_lambda + 280
23  Emacs                                 0x100957da8 eval_sub + 1264
24  Emacs                                 0x1009581c8 Fand + 60
25  Emacs                                 0x100957f7c eval_sub + 1732
26  Emacs                                 0x1009593f0 FletX + 268
27  Emacs                                 0x100957f7c eval_sub + 1732
28  Emacs                                 0x100957ed0 eval_sub + 1560
29  Emacs                                 0x100957ed0 eval_sub + 1560
30  Emacs                                 0x100957ed0 eval_sub + 1560
31  Emacs                                 0x10095824c Fprogn + 48
32  Emacs                                 0x10095d728 funcall_lambda + 1276
33  Emacs                                 0x10095c284 apply_lambda + 280
34  Emacs                                 0x100957da8 eval_sub + 1264
35  Emacs                                 0x10095974c Flet + 316
36  Emacs                                 0x100957f7c eval_sub + 1732
37  Emacs                                 0x100958034 eval_sub + 1916
38  Emacs                                 0x10095824c Fprogn + 48
39  Emacs                                 0x10095d728 funcall_lambda + 1276
40  Emacs                                 0x100959dc8 Ffuncall + 316
41  Emacs                                 0x100958074 eval_sub + 1980
42  Emacs                                 0x10095824c Fprogn + 48
43  Emacs                                 0x100957f7c eval_sub + 1732
44  Emacs                                 0x10095824c Fprogn + 48
45  Emacs                                 0x10095d728 funcall_lambda + 1276
46  Emacs                                 0x100959dc8 Ffuncall + 316
47  Emacs                                 0x1009677d4 mapcar1 + 328
48  Emacs                                 0x1009675b4 Fmapconcat + 460
49  Emacs                                 0x1009580d8 eval_sub + 2080
50  Emacs                                 0x1009593f0 FletX + 268
51  Emacs                                 0x100957f7c eval_sub + 1732
52  Emacs                                 0x10095c070 Feval + 84
53  Emacs                                 0x100959dc8 Ffuncall + 316
54  Emacs                                 0x10095ab74
internal_condition_case_n + 156
55  Emacs                                 0x100842d84 safe__call + 296
56  Emacs                                 0x100842e40 safe__call1 + 36
57  Emacs                                 0x100842e68
safe_eval_inhibit_quit + 28
58  Emacs                                 0x10088d47c
null_header_line_format + 388
59  Emacs                                 0x100881800
window_wants_header_line + 296
60  Emacs                                 0x100839e0c window_box_height + 860
61  Emacs                                 0x100829838
required_matrix_height + 72
62  Emacs                                 0x100829908
allocate_matrices_for_window_redisplay + 148
63  Emacs                                 0x100823728 adjust_frame_glyphs + 88
64  Emacs                                 0x10088f638
Fset_window_configuration + 4068
65  tab-bar-f81d329c-3b6a0fc2.eln        0x107163bc8
F7461622d6261722d73656c6563742d746162_tab_bar_select_tab_0 + 868
66  Emacs                                 0x100959dc8 Ffuncall + 316
67  tab-bar-f81d329c-3b6a0fc2.eln        0x1071641d4
F7461622d6261722d7377697463682d746f2d6e6578742d746162_tab_bar_switch_to_next_tab_0
+ 260
68  Emacs                                 0x100959dc8 Ffuncall + 316
69  Emacs                                 0x10095592c
Ffuncall_interactively + 68
70  Emacs                                 0x100959dc8 Ffuncall + 316
71  Emacs                                 0x100956a08 Fcall_interactively + 4292
72  simple-fab5b0cf-e1c8f2a9.eln         0x102b54b0c
F636f6d6d616e642d65786563757465_command_execute_0 + 652