let join t1 t2 =
(*
{
initialized = t1.initialized && t2.initialized;
no_escaping_adr = t1.no_escaping_adr && t2.no_escaping_adr;
v = V.join t1.v t2.v
}
*)
create
((get_flags t1) land (get_flags t2))
(V.join (get_v t1) (get_v t2))