+ 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 free_access_inv_None m b lo hi m' (FR: Mem.free m b lo hi = Some m') b' ofs k
(P: (Mem.mem_access m') !! b' ofs k = None):
(b' = b /\ Z.le lo ofs /\ Z.lt ofs hi /\  (Mem.mem_access m) !! b' ofs k = Some Freeable) \/
((b' <> b \/ Z.lt ofs lo \/ Z.le hi ofs) /\ (Mem.mem_access m) !! b' ofs k = None).