Definition getBlocks (V:list val) (b: block): bool :=
   in_dec eq_block b
    (fold_right (fun v L => match v with Vptr b' z => b'::L | _ => L end) nil V).

Lemma getBlocksD: forall v V b, getBlocks (v:: V) b = match v with Vptr b' _ => orb (eq_block b' b) (getBlocks V b) | _ => getBlocks V b end.