(*TODO: Move to ev_semantics*)
    Definition in_free_list (b : block) ofs xs :=
      exists x, List.In x xs /\
           let '(b', lo, hi) := x in
           b = b' /\
           (lo <= ofs < hi)%Z.

Lemma free_list_valid_block: forall m m' l b, Mem.free_list m l = Some m' -> Mem.valid_block m b <-> Mem.valid_block m' b.