Hint Resolve list_rep_Xlist_valid_pointer: valid_pointer.

Lemma list_rep_Xlist_local_facts:
forall (r: list val) (q: val),
list_rep (fun (p: val) (n: val) (q: val) => data_at Tsh t_struct_Xlist (p, n) q) r q |-- !! (is_pointer_or_null q  /\ (q=nullval <-> r=nil)).