bug#9436: 24.0.50; Segmentation fault during redisplay

[Eli Zaretskii]

> From: Helmut Eller <eller.helmut@gmail.com>
> Date: Mon, 05 Sep 2011 00:35:34 +0200
> 
> I updated the source tree and configured with
> `configure  '--with-gif=no' '--with-gnutls=no' 'CFLAGS=-g3 -O0''

Please reconfigure like this:

  configure --enable-asserts --enable-checking --with-gif=no --with-gnutls=no 
'CFLAGS=-g3 -O0'

This will enable several important sanity checks and hopefully allow
us to see why the frame pointer is NULL.  Please try again after
rebuilding Emacs, and see if you get an abort somewhere, or the same
segfault.

> Then started Emacs from gdb.  After a while the it occurred again.
> it->f seems to be 0 here too:
> 
> (gdb) frame 0
> #0  0x0807e455 in move_it_to (it=0xbfffd9d0, to_charpos=1688, to_x=-1, 
>     to_y=-1, to_vpos=-1, op=8) at xdisp.c:8444
> 8444      if (!FRAME_WINDOW_P (it->f)
> (gdb) p it->f
> $5 = (struct frame *) 0x0

If you go up 1 frame to here:

> #1  0x080865e7 in redisplay_internal () at xdisp.c:12814

And display w->frame there, is it also NULL?  If so, can you display
the contents of the structure pointed to by w, and also compare that
with selected_window?  Also, what is the value of current_buffer and
selected_frame?

When this happened, is it possible that you did something that
modified the display configuration, like killed a window or a frame or
changed the display dimensions?