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 load_storebytes_nil m b ofs m': Mem.storebytes m b ofs nil = Some m' -> forall ch bb z, Mem.load ch m' bb z = Mem.load ch m bb z.