Instance CompSpecs : compspecs. make_compspecs prog. Defined.
Definition Vprog : varspecs. mk_varspecs prog. Defined.
Instance LS: listspec _list _tail (fun _ _ => emp).

Lemma butlast_fold h t : match t with [] => [] | _ :: _ => h :: butlast t end = butlast (h :: t). Proof. auto. Qed.