Hint Rewrite ptr_eq_True using solve[auto] : norm.

(* Specifications: *)
Lemma ptr_eq_is_pointer_or_null: forall x y, ptr_eq x y -> is_pointer_or_null x.
Lemma ptr_eq_sym: forall x y, ptr_eq x y -> ptr_eq y x.
Lemma ptr_eq_trans: forall x y z, ptr_eq x y -> ptr_eq y z -> ptr_eq x z.
Lemma isptr_offset_val_zero:
forall v, isptr v -> offset_val 0 v = v.