bug#7348: 23.2.50; Emacs crashes on fast window resize with scrollbars on under OSX

[YAMAMOTO Mitsuharu]

>>>>> On Sun, 07 Nov 2010 11:34:24 +0100, martin rudalics <rudalics@gmx.at> 
>>>>> said:

>> The value of w->buffer was nil when the assertion failure occurred.

> IIUC this means the selected window was deleted and not replaced by
> another window.  Can you check whether this is already the case at
> the time redisplay_internal is entered?

That's not the case at the beginning of redisplay_internal, indeed.
The call to do_pending_window_change at line 11397 in xdisp.c
(emacs-23 branch) seems to change selected_window because of the
following call chain, but the variable `w' in redisplay_internal still
points to the old selected window.

  redisplay_internal
    -> do_pending_window_change
      -> change_frame_size
        -> change_frame_size_1
          -> set_window_height
            -> size_window
              -> delete_window (/* Delete WINDOW if it's too small.  */)

                                     YAMAMOTO Mitsuharu
                                mituharu@math.s.chiba-u.ac.jp