(** Preservation of [free] operations *)

Lemma drop_outside_inject: forall f m1 m2 b lo hi p m2',
inject f m1 m2 ->
drop_perm m2 b lo hi p = Some m2' ->
(forall b' delta ofs k p,
f b' = Some(b, delta) ->
perm m1 b' ofs k p -> lo <= ofs + delta < hi -> False) ->
inject f m1 m2'.