let link_vtable_to_db = fun vtable ->
let db = vtable.vt_db in
List.iter
(fun vt -> assert (vt != vtable); (* Physical eq *)
if vtable.vt_name = vt.vt_name then
raise (Duplicated_name vtable.vt_name))
db.db_vtables;
db.db_vtables <- db.db_vtables @ [vtable]