Definition val_inject_opt (j: meminj) (v1 v2: option val) :=
  match v1, v2 with Some v1', Some v2' => val_inject j v1' v2'
  | None, None => True
  | _, _ => False
  end.

Lemma forall_val_inject_flat: forall m1 m2 j (Inj: Mem.inject j m1 m2) vals1 vals2 (V: Forall2 (val_inject j) vals1 vals2), Forall2 (val_inject (Mem.flat_inj (Mem.nextblock m1))) vals1 vals1.