Crash in show_busy_cursor.

[Jason Rumney]

Having given up on dbx and installed gdb, I found that the crash I
reported earlier occurred on the line marked "==>", with f = 0.
Since earlier lines have successfully dereferenced f, I suspect some
stack corruption has occurred, possibly due to non-reentrant system
library functions as Eli suggested.

Note though that it is possible for a NULL pointer to pass the
FRAME_X_P test if the right byte just happens to be found at that
location, so maybe (f != 0) should be added to that test (and other
similar tests).


static void
show_busy_cursor (timer)
     struct atimer *timer;
{
  /* The timer implementation will cancel this timer automatically
     after this function has run.  Set busy_cursor_atimer to null
     so that we know the timer doesn't have to be canceled.  */
  busy_cursor_atimer = NULL;

  if (!busy_cursor_shown_p)
    {
      Lisp_Object rest, frame;
  
      BLOCK_INPUT;
  
      FOR_EACH_FRAME (rest, frame)
        if (FRAME_X_P (XFRAME (frame)))
          {
            struct frame *f = XFRAME (frame);
        
            f->output_data.x->busy_p = 1;
        
            if (!f->output_data.x->busy_window)
              {
                unsigned long mask = CWCursor;
                XSetWindowAttributes attrs;
            
                attrs.cursor = f->output_data.x->busy_cursor;
            
==>             f->output_data.x->busy_window
                  = XCreateWindow (FRAME_X_DISPLAY (f),
                                   FRAME_OUTER_WINDOW (f),
                                   0, 0, 32000, 32000, 0, 0,
                                   InputOnly,
                                   CopyFromParent,
                                   mask, &attrs);
              }
        
            XMapRaised (FRAME_X_DISPLAY (f), f->output_data.x->busy_window);
            XFlush (FRAME_X_DISPLAY (f));
          }

      busy_cursor_shown_p = 1;
      UNBLOCK_INPUT;
    }
}

-- 
Jason Rumney <address@hidden>
AT&T Labs (Redditch, UK)

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