(** The values of the erased memory may be more defined and its
       permissions are top.*)
  (** In retrospect setting the permissions to top was a bad
  choice. It should have been that the permissions of the erased
  memory are above the permissions of the other memory. This would
  make it more reusable and it wouldn't need a second definition for
  free. *)

  Local Notation "a # b" := (PMap.get b a) (at level 1).

Lemma storebytes_erasure: forall m m' b ofs mv mv' m2 (Hstore: Mem.storebytes m b ofs mv = Some m2) (Herased: mem_erasure m m') (Hval_erasure: memval_erasure_list mv mv') , exists m2', Mem.storebytes m' b ofs mv' = Some m2' /\ mem_erasure m2 m2'.