Subject: bug#10159: auto-complete causes crash in emacs HEAD

From: Eli Zaretskii <[email-masked]>
Date: Sat, 22 Sep 2012 14:58:17 +0300

> From: Christopher Monsanto <[email-masked]>
> Date: Sat, 22 Sep 2012 07:12:45 -0400
> 
> Sorry, there should not be a space in "def ". "def" is what will do it.

Neither "def " nor "def" reproduce the crash for me.  But I succeeded
in reproducing a very similar crash anyway.  The problem seems to be
that the display code runs off the end of an overlay string.  To
verify that this is what happens to you as well, please do

 (gdb) frame 1
 (gdb) pp string

(If 'pp' doesn't work, you will need to type

 (gdb) source /path/to/emacs/src/.gdbinit

to make that command available to GDB.)

You should see that 'string' is shorter than 43 characters, whereas
this part of your backtrace:

  #1  0x0000000000663076 in composition_compute_stop_pos (cmp_it=0x7fffffff9148, charpos=43, bytepos=44, endpos=43, string=25414881)
      at composite.c:1053

indicates that the code attempted to access character number 43.

In my case, 'charpos' is 41, 'bytepos' is 42, and 'string' is 36
characters long.

I'm looking into the cause of this bug.