(* No unvalid pointers, i.e. othing pointing after nextblock *)
Definition mem_wd (m:mem):=
inject_neutral (nextblock m) m.
(* All arguments are in memory and without unvalid pointers*)
Definition arg_well_formed args m0:=
Val.inject_list (flat_inj (nextblock m0)) args args.
Remark mem_wd_inject:
forall m, mem_wd m -> inject (flat_inj (nextblock m)) m m.

Theorem drop_inject_neutral:
forall m b lo hi p m' thr,
drop_perm m b lo hi p = Some m' ->
inject_neutral thr m ->
Plt b thr ->
inject_neutral thr m'.