+ intros. xomega.
+ induction 1.
- apply Mem.nextblock_storebytes in H;
rewrite H; xomega.
- apply Mem.nextblock_alloc in H.
rewrite H. clear. xomega.
- apply nextblock_freelist in H.
rewrite H; xomega.
- xomega.
Qed.

Lemma alloc_access_inv_None m b lo hi m' (ALLOC: Mem.alloc m lo hi = (m', b)) b' ofs k
(P: (Mem.mem_access m') !! b' ofs k = None): (Mem.mem_access m) !! b' ofs k = None.