Definition block_ok (b: block) := Plt b nextb.Definition val_ok (v: val) : Prop := 
 match v with
 | Vptr b _ => block_ok b
 | _ => True
 end.Definition venv_ok (ve: Clight.env) :=
  forall i bt, PTree.get i ve = Some bt -> block_ok (fst bt).Definition tenv_ok (te: Clight.temp_env) :=
  forall i (v: val), PTree.get i te = Some v -> val_ok v.Definition cont'_ok (k: Clight_new.cont') := 
 match k with
 | Clight_new.Kcall _ _ ve te => venv_ok ve /\ tenv_ok te
 | _ => True
 end.Definition cont_ok (k: Clight_new.cont) := Forall cont'_ok k.Definition corestate_ok (q: Clight_new.corestate) : Prop :=
 match q with
 | Clight_new.State ve te k => venv_ok ve /\ tenv_ok te /\ cont_ok k
 | Clight_new.ExtCall f vl _ ve te k => Forall val_ok vl /\ venv_ok ve /\ tenv_ok te /\ cont_ok k
 end.

Lemma set_venv_ok: forall nextb i v ve, block_ok nextb (fst v) -> venv_ok nextb ve -> venv_ok nextb (PTree.set i v ve).