End CENV.
Hint Extern 2 (memory_block _ _ _ |-- valid_pointer _) =>
(apply memory_block_valid_ptr; [auto with valid_pointer | rep_omega]) : valid_pointer.

(* Specifications: *)
Lemma valid_pointer_weak:
forall a, valid_pointer a |-- weak_valid_pointer a.
Lemma valid_pointer_weak':
forall P q, P |-- valid_pointer q ->
P |-- weak_valid_pointer q.