Definition check_gvars_spec (GV: option globals) (GV': option globals) : Prop :=
  match GV' with Some _ => GV = GV' | _ => True end.Definition strong_cast (t1 t2: type) (v: val) : val :=
 force_val (sem_cast t1 t2 v).

Lemma extract_trivial_liftx_e: forall (R: list (environ->mpred)) (R': list mpred), extract_trivial_liftx R R' -> R = map liftx R'.