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.

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.