bug#30519: 26.0.91; Emacs hangs with flyspell overlay

[Nick Helm <nick@tenpoint.co.nz>]

On Tue, 20 Feb 2018 at 17:06:00 +1300, Eli Zaretskii wrote:

> A C- and Lisp-level backtrace from the place which signals that error
> would be helpful.

Another from Ubuntu 17 / GTK.

(gdb) bt
#0  0x00000000005e25ec in marker_position (marker=XIL(0x376b469)) at marker.c:641
#1  0x00000000005ced7e in mouse_face_overlay_overlaps (overlay=XIL(0x376b4e1)) at buffer.c:3058
#2  0x00000000004a943f in note_mouse_highlight (f=0x1603c80 <bss_sbrk_buffer+8226176>, x=170, y=120) at xdisp.c:31349
#3  0x0000000000540904 in XTframe_up_to_date (f=0x1603c80 <bss_sbrk_buffer+8226176>) at xterm.c:1291
#4  0x000000000046a893 in redisplay_internal () at xdisp.c:14505
#5  0x000000000046abc8 in redisplay_preserve_echo_area (from_where=5) at xdisp.c:14617
#6  0x000000000059c4fc in read_char (commandflag=1, map=XIL(0x124dcc3), prev_event=XIL(0), used_mouse_menu=0x7fffffffe101, end_time=0x0) at keyboard.c:2478
#7  0x00000000005acd97 in read_key_sequence (keybuf=0x7fffffffe2a0, bufsize=30, prompt=XIL(0), dont_downcase_last=false, can_return_switch_frame=true, fix_current_buffer=true, prevent_redisplay=false) at keyboard.c:9147
#8  0x0000000000598ed0 in command_loop_1 () at keyboard.c:1368
#9  0x0000000000653d0d in internal_condition_case (bfun=0x598a6e <command_loop_1>, handlers=XIL(0x5250), hfun=0x598093 <cmd_error>) at eval.c:1332
#10 0x0000000000598689 in command_loop_2 (ignore=XIL(0)) at keyboard.c:1110
#11 0x00000000006531c8 in internal_catch (tag=XIL(0xc6f0), func=0x59865c <command_loop_2>, arg=XIL(0)) at eval.c:1097
#12 0x0000000000598627 in command_loop () at keyboard.c:1089
#13 0x0000000000597b7d in recursive_edit_1 () at keyboard.c:695
#14 0x0000000000597d72 in Frecursive_edit () at keyboard.c:766
#15 0x000000000059575e in main (argc=1, argv=0x7fffffffe6f8) at emacs.c:1713

Lisp Backtrace:
"redisplay_internal (C function)" (0x0)
(gdb)