(** Memory states that inject into themselves. *)
Definition flat_inj (thr: block) : meminj :=
fun (b: block) => if plt b thr then Some(b, 0) else None.
Parameter inject_neutral: forall (thr: block) (m: mem), Prop.

Axiom alloc_inject_neutral:
forall thr m lo hi b m',
alloc m lo hi = (m', b) ->
inject_neutral thr m ->
Plt (nextblock m) thr ->
inject_neutral thr m'.