Definition padding_freeable (f: meminj) (e: Csharpminor.env) (tm: mem) (sp: block) (sz: Z) : Prop :=
  forall ofs,
  0 <= ofs < sz -> Mem.perm tm sp ofs Cur Freeable \/ is_reachable_from_env f e sp ofs.

(* Specifications: *)
Lemma padding_freeable_invariant: forall f1 e tm1 sp sz cenv lo hi f2 tm2, padding_freeable f1 e tm1 sp sz -> match_env f1 cenv e sp lo hi -> (forall ofs, Mem.perm tm1 sp ofs Cur Freeable -> Mem.perm tm2 sp ofs Cur Freeable) -> (forall b, Plt b hi -> f2 b = f1 b) -> padding_freeable f2 e tm2 sp sz.
Lemma is_reachable_from_env_dec: forall f e sp ofs, is_reachable_from_env f e sp ofs \/ ~is_reachable_from_env f e sp ofs.