Overlay problems solved (maybe partially)

[Gerd Moellmann]

I've added asssertions to buffer.c because some new code in
move_overlay looked dubious to me:

--- buffer.c.~1.435.~   Mon Aug 11 13:16:29 2003
+++ buffer.c    Mon Aug 18 14:05:45 2003
@@ -3743,13 +3743,17 @@
     {
       if (b->overlays_after)
        XOVERLAY (overlay)->next = b->overlays_after;
-    b->overlays_after = XOVERLAY (overlay);
+      else
+       eassert (XOVERLAY (overlay)->next == NULL);
+      b->overlays_after = XOVERLAY (overlay);
     }
   else
     {
       if (b->overlays_before)
        XOVERLAY (overlay)->next = b->overlays_before;
-    b->overlays_before = XOVERLAY (overlay);
+      else
+       eassert (XOVERLAY (overlay)->next == NULL);
+      b->overlays_before = XOVERLAY (overlay);
     }
 
   /* This puts it in the right list, and in the right order.  */

The new assertion was just triggered, which nicely explains the
overlay problems I'm experiencing.

I've committed a fix to CVS (and I'm surprised that still works :).