Notation val_inject:=Val.inject.
(*A value that is (if its a pointer) not dangling wrt m - a condition like this will probably be need to imposed on after-external return values (and thus also on the values returned by halted)*)
Definition val_valid (v:val) (m:mem):Prop :=
match v with Vptr b ofs => Mem.valid_block m b | _ => True
end.
(*memories that do not contain "dangling pointers"*)
Definition mem_wd m := Mem.inject_neutral (Mem.nextblock m) m.

Lemma free_neutral: forall (thr : block) (m : mem) (lo hi : Z) (b : block) (m' : Mem.mem')
(FREE: Mem.free m b lo hi = Some m'),
Mem.inject_neutral thr m -> Mem.inject_neutral thr m'.