Corollary wf_table_upd_same : forall T k v i (Hwf : wf_table T) (HT : Zlength T = size)
  (Hi : fst (Znth i T) = k) (Hk : k <> 0), wf_table (upd_Znth i T (k, v)).

Lemma lock_struct : forall p, data_at_ Tsh (Tstruct _lock_t noattr) p = data_at_ Tsh tlock p.