bug#59183: 29.0.50; emacs_abort () at sysdep.c:2313

[Eli Zaretskii <eliz@gnu.org>]

> From: Gregor Zattler <telegraph@gmx.net>
> Date: Thu, 10 Nov 2022 19:55:07 +0100
> 
> Dear Emacs developers, Emacs aborted, just while selected
> some text with the mouse:
> 
> 
> Thread 1 "emacs" hit Breakpoint 1, terminate_due_to_signal (sig=6, backtrace_limit=40) at emacs.c:421
> 421	{
> #0  terminate_due_to_signal (sig=6, backtrace_limit=40) at emacs.c:421
> #1  0x000055555579def5 in emacs_abort () at sysdep.c:2313
> #2  0x00005555559324d6 in itree_iterator_start (tree=0x555556e65850, begin=359683, end=592913, order=ITREE_ASCENDING, file=0x5555559eca4f "buffer.c", line=2982) at itree.c:1161
> #3  0x00005555557ae9ef in overlays_in (beg=359683, end=359684, extend=false, vec_ptr=0x7fffffff18c0, len_ptr=0x7fffffff1910, empty=false, trailing=true, next_ptr=0x0) at buffer.c:2982
> #4  0x00005555557aebed in overlays_at (pos=359683, extend=false, vec_ptr=0x7fffffff18c0, len_ptr=0x7fffffff1910, next_ptr=0x0) at buffer.c:3035
> #5  0x0000555555646226 in note_mouse_highlight (f=0x5555590388f0, x=181, y=321) at xdisp.c:35144
> #6  0x000055555570b846 in x_note_mouse_movement (frame=0x5555590388f0, event=0x7fffffff1f20, device=XIL(0x5555563b5cd4)) at xterm.c:14137
> #7  0x000055555571ab35 in handle_one_xevent (dpyinfo=0x55555a326240, event=0x7fffffff2380, finish=0x7fffffff2370, hold_quit=0x7fffffff24a0) at xterm.c:22381
> #8  0x000055555571f577 in XTread_socket (terminal=0x5555572511a0, hold_quit=0x7fffffff24a0) at xterm.c:24551
> #9  0x000055555577d39a in gobble_input () at keyboard.c:7368
> #10 0x000055555577d997 in handle_async_input () at keyboard.c:7599
> #11 0x000055555577d9b6 in process_pending_signals () at keyboard.c:7613
> #12 0x00005555558580cb in probably_quit () at eval.c:1661
> #13 0x000055555586383d in maybe_quit () at lisp.h:3684
> #14 0x000055555586ac7c in Fassq (key=XIL(0x5d00), alist=XIL(0x5555594ef1f3)) at fns.c:1931
> #15 0x000055555590c41d in lookup_char_property (plist=XIL(0x555560375da3), prop=XIL(0x5d00), textprop=false) at intervals.c:1735
> #16 0x00005555557b1dc8 in Foverlay_get (overlay=XIL(0x555560371dcd), prop=XIL(0x5d00)) at buffer.c:3934
> #17 0x0000555555911dc1 in get_char_property_and_overlay (position=make_fixnum(359631), prop=XIL(0x5d00), object=XIL(0x55555e02d465), overlay=0x7fffffff2768) at textprop.c:649

Stefan, I think we must lift the restriction of "only one itree
iteration at a time", otherwise we will keep bumping into situations
like this one.  It isn't hard to imagine other cases where some code
wants to look up overlays while some of the callers is in the middle
of something similar; handling the mouse-highlight is just one such
example.  We never had restrictions in Emacs on simultaneous multiple
read-only access to overlays, and it makes no sense to introduce such
restrictions now.

This has to be fixed before Emacs 29.