bug#60144: 30.0.50; PGTK Emacs crashes after signal

[Eli Zaretskii]

> Cc: 60144@debbugs.gnu.org
> Date: Sun, 18 Dec 2022 10:08:59 +0800
> From:  Po Lu via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> Karl Otness <karl@karlotness.com> writes:
> 
> >> #0  Fsignal (error_symbol=error_symbol@entry=0x2f40, data=0x55bed53eeac3) 
> >> at eval.c:1681
> >> #1  0x000055bece1213bf in xsignal (data=<optimized out>, 
> >> error_symbol=0x2f40) at emacs/src/lisp.h:4558
> >> #2  xsignal1 (error_symbol=error_symbol@entry=0x2f40, arg=arg@entry=0x82) 
> >> at eval.c:1878
> >> #3  0x000055bece1253e3 in get_char_property_and_overlay (position=0x82, 
> >> prop=0x5a90, object=0x7f105451a265, overlay=0x0) at textprop.c:644
> >> #4  0x000055bece156110 in string_buffer_position_lim 
> >> (string=string@entry=0x55bed52e8b24, from=from@entry=32, to=to@entry=1032, 
> >> back_p=back_p@entry=false) at xdisp.c:6246
> >> #5  0x000055bece1561fa in string_buffer_position (string=0x55bed52e8b24, 
> >> around_charpos=32) at xdisp.c:6284
> >> #6  0x000055bece1aaddb in note_mouse_highlight (f=f@entry=0x55bed1a839e8, 
> >> x=<optimized out>, y=<optimized out>) at xdisp.c:35339
> >> #7  0x000055bece4039ac in note_mouse_movement (event=0x55bed1ce6030, 
> >> frame=0x55bed1a839e8) at pgtkterm.c:5821
> >> #8  motion_notify_event (widget=widget@entry=0x55bed2024130, 
> >> event=0x55bed1ce6030, user_data=<optimized out>) at pgtkterm.c:5905
> >> #9  0x00007f105c684fd8 in _gtk_marshal_BOOLEAN__BOXED 
> >> (closure=0x55bed1ef9f40, return_value=0x7ffebc5ae480, 
> >> n_param_values=<optimized out>, param_values=0x7ffebc5ae4e0, 
> >> invocation_hint=<optimized out>, marshal_data=<optimized out>)
> >>     at gtk/gtkmarshalers.c:84
> >> #10 0x00007f105c095210 in g_closure_invoke (closure=0x55bed1ef9f40, 
> >> return_value=0x7ffebc5ae480, n_param_values=2, 
> >> param_values=0x7ffebc5ae4e0, invocation_hint=0x7ffebc5ae460) at 
> >> ../glib/gobject/gclosure.c:832
> >> #11 0x00007f105c0c2ea8 in signal_emit_unlocked_R.isra.0
> >>     (node=<optimized out>, detail=detail@entry=0, 
> >> instance=instance@entry=0x55bed2024130, 
> >> emission_return=emission_return@entry=0x7ffebc5ae5f0, 
> >> instance_and_params=instance_and_params@entry=0x7ffebc5ae4e0)
> >>     at ../glib/gobject/gsignal.c:3796
> >> #12 0x00007f105c0b2980 in g_signal_emit_valist (instance=<optimized out>, 
> >> signal_id=<optimized out>, detail=<optimized out>, 
> >> var_args=var_args@entry=0x7ffebc5ae6a0) at ../glib/gobject/gsignal.c:3559
> >> #13 0x00007f105c0b3204 in g_signal_emit 
> >> (instance=instance@entry=0x55bed2024130, signal_id=<optimized out>, 
> >> detail=detail@entry=0) at ../glib/gobject/gsignal.c:3606
> >> #14 0x00007f105c9447f5 in gtk_widget_event_internal.part.0.lto_priv.0 
> >> (widget=0x55bed2024130, event=0x55bed1ce6030) at 
> >> ../gtk/gtk/gtkwidget.c:7812
> >> #15 0x00007f105c7e20db in propagate_event_up (topmost=<optimized out>, 
> >> event=<optimized out>, widget=0x55bed2024130) at ../gtk/gtk/gtkmain.c:2588
> >> #16 propagate_event (widget=widget@entry=0x55bed2024130, 
> >> event=event@entry=0x55bed1ce6030, captured=captured@entry=0, 
> >> topmost=topmost@entry=0x0) at ../gtk/gtk/gtkmain.c:2691
> >> #17 0x00007f105c7e2212 in gtk_propagate_event 
> >> (widget=widget@entry=0x55bed2024130, event=event@entry=0x55bed1ce6030) at 
> >> ../gtk/gtk/gtkmain.c:2725
> >> #18 0x00007f105c7e2fbb in gtk_main_do_event (event=<optimized out>) at 
> >> ../gtk/gtk/gtkmain.c:1921
> >> #19 gtk_main_do_event (event=<optimized out>) at ../gtk/gtk/gtkmain.c:1691
> >> #20 0x00007f105c542cd3 in _gdk_event_emit (event=0x55bed1ce6030) at 
> >> ../gtk/gdk/gdkevents.c:73
> >> #21 _gdk_event_emit (event=0x55bed1ce6030) at ../gtk/gdk/gdkevents.c:67
> 
> Thanks.  This sounds awfully like another bug that was fixed last month.
> Would someone please take a look at this? note_mouse_highlight should
> never signal.

You cannot require that from note_mouse_highlight, since it looks up
text and overlay properties, and those can signal an error if the
position is outside the valid/reachable range of buffer positions.

Do you understand why note_mouse_highlight was called in this
scenario?  The backtrace seems strange: why should GTK care about our
mouse highlight?