truct (Memory.Mem.weak_valid_pointer m b (Ptrofs.unsigned i)) eqn:?;
  simpl in H; inv H.
-

`(a && b) (make_args d e) = `a (make_args d e) && `b (make_args d e). Proof. intros. reflexivity. Qed. Hint Rewrite andp_makeargs: norm2.