let unlink_vtable = fun vtable ->
let (vtables, to_be_removed) =
List.partition (fun vt -> vt.vt_name <> vtable.vt_name)
vtable.vt_db.db_vtables
in
vtable.vt_db.db_vtables <- vtables;
match to_be_removed with
| [vt] -> vt.vt_db <- (Obj.magic 0)
| _ -> Dbf_misc.ie ()