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

Lemma list_append_null (cs : compspecs)
(list_structid list_link : ident) (sh : share)
(ls : listspec list_structid list_link list_token) (hd mid : val)
(ct1 ct2 : list (elemtype ls)) :
lseg ls sh ct1 hd mid * lseg ls sh ct2 mid nullval
|-- lseg ls sh (ct1 ++ ct2) hd nullval.