Definition inj_offset_aligned (delta: Z) (size: Z) : Prop :=
forall chunk, size_chunk chunk <= size -> (align_chunk chunk | delta).

Axiom free_parallel_inject:
forall f m1 m2 b lo hi m1' b' delta,
inject f m1 m2 ->
free m1 b lo hi = Some m1' ->
f b = Some(b', delta) ->
exists m2',
free m2 b' (lo + delta) (hi + delta) = Some m2'
/\ inject f m1' m2'.