Ltac make_Vptr c :=
  let H := fresh in assert (isptr c) by auto;
  destruct c; try (contradiction H); clear H.

(* Specifications: *)
Lemma Zmax0r: forall n, 0 <= n -> Z.max 0 n = n.
Lemma cstringn_equiv : forall {CS : compspecs} sh s p, cstring sh s p = cstringn sh s (Zlength s + 1) p.