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_range: forall n ofs M bytes1 v bytes2, Mem.getN n ofs M = bytes1 ++ v::bytes2 -> (length bytes1 < n)%nat.