bug#11351: 24.1.50; marker does not point anywhere

[Eli Zaretskii <eliz@gnu.org>]

> From: Sam Steingold <sds@gnu.org>
> Date: Thu, 26 Apr 2012 09:29:37 -0400
> 
> Lisp Backtrace:
> "recursive-edit" (0xffffb5c8)
> "debug" (0xffffb858)
> 
> emacs displays the *Backtrace* buffer with a single line:
> 
> debugger entered--lisp error: (error "Marker does not point anywhere")

Is this error always shown when this happens?  If so, what markers
could be involved? what were you doing when this happens?

This part of the C backtrace seems to indicate that some overlay is
involved that specifies its own keymap:

#24 0x000000000051dcc4 in marker_position (marker=<optimized out>) at /home/sds/src/emacs/trunk/src/marker.c:777
#25 0x0000000000514667 in overlays_at (pos=77003, extend=0, vec_ptr=0x7fffffffccd8, len_ptr=0x7fffffffcce0, next_ptr=0x0, prev_ptr=0x0, change_req=0)
    at /home/sds/src/emacs/trunk/src/buffer.c:2541
#26 0x00000000005bc60f in get_char_property_and_overlay (position=308012, prop=12156402, object=43556693, overlay=0x0)
    at /home/sds/src/emacs/trunk/src/textprop.c:626
#27 0x00000000005b9756 in get_local_map (position=<optimized out>, buffer=0x2989f50, type=12156402) at /home/sds/src/emacs/trunk/src/intervals.c:2306
#28 0x00000000004febe7 in read_key_sequence (keybuf=0x7fffffffcf40, prompt=11966850, dont_downcase_last=0, can_return_switch_frame=1, 
    fix_current_buffer=1, bufsize=30) at /home/sds/src/emacs/trunk/src/keyboard.c:9147

Do you have any guesses as to what that overlay might be?