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 getN_aux: forall n p c B1 v B2, Mem.getN n p c = B1 ++ v::B2 -> v = ZMap.get (p + Z.of_nat (length B1)) c.