Hi,
I tried to get more info by setting a breakpoint in redisplay-x.c,
line 482. Here is the GDB backtrace (I hope you find it useful):
Breakpoint 1, x_output_display_block (w=0x733800, dl=0x83f370, block=0,
start=6, end=1, start_pixpos=4, cursor_start=184, cursor_width=5,
cursor_height=14) at redisplay-x.c:482
(gdb) where
#0 x_output_display_block (w=0x733800, dl=0x83f370, block=0, start=6, end=1,
start_pixpos=4, cursor_start=184, cursor_width=5, cursor_height=14)
at redisplay-x.c:482
#1 0x1ae138 in redisplay_output_display_block (w=0x733800, dl=0x83f370,
block=0, start=6, end=1, start_pixpos=14, cursor_start=184,
cursor_width=5, cursor_height=14) at redisplay-output.c:1134
#2 0x1ad1d8 in output_display_line (w=0x733800, cdla=0x71ece0, ddla=0x71ecc0,
line=10, force_start=4, force_end=724) at redisplay-output.c:802
#3 0x1b1674 in redisplay_output_window (w=0x733800) at redisplay-output.c:2256
#4 0x1a1884 in redisplay_window (window=7550976, skip_selected=2739)
at redisplay.c:6212
#5 0x1a1ee8 in redisplay_frame (f=0x3a4c00, preemption_check=0)
at redisplay.c:6424
#6 0x1a2154 in redisplay_device (d=0x629e00, automatic=3820544)
at redisplay.c:6502
#7 0x1a26d4 in redisplay_without_hooks () at redisplay.c:6591
#8 0x1a2954 in redisplay () at redisplay.c:6648
#9 0xfc564 in Fnext_event (event=6544060, prompt=3131396)
at event-stream.c:2180
#10 0x88444 in Fcommand_loop_1 () at cmdloop.c:566
#11 0x88194 in command_loop_1 (dummy=3131396) at cmdloop.c:490
#12 0xa9ff4 in condition_case_1 (handlers=3131492,
bfun=0x88148 <command_loop_1>, barg=3131396, hfun=0x875f8 <cmd_error>,
---Type <return> to continue, or q <return> to quit---
harg=3131396) at eval.c:1644
#13 0x8770c in command_loop_3 () at cmdloop.c:252
#14 0x8772c in command_loop_2 (dummy=3131396) at cmdloop.c:263
#15 0xa9adc in internal_catch (tag=3213556, func=0x87720 <command_loop_2>,
arg=3131396, threw=0x0) at eval.c:1310
#16 0x87a90 in initial_command_loop (load_me=554784) at cmdloop.c:301
#17 0xa52ac in sort_args (argc=2921472, argv=0xeffff0dc) at emacs.c:1873
(gdb)
...
(gdb) p instance
$7 = 8641920
(gdb)
Cheers, Uli