Section CENV.
Context {cs: compspecs}.
Definition union_default_filter m :=
match m with
| nil => fun _ => false
| hd :: _ => fun m => if member_dec hd m then true else false
end.
Definition is_default_filter {A} f (l: list A) :=
match l with
| nil => True
| hd :: _ => f hd = true
end.
(* Lemma union_default_filter_legal: forall m, m <> nil -> legal_compact_sum_filter (union_default_filter m) m = true. *)
Definition struct_default_val (m : members) := compact_prod_gen (fun it => default_val (field_type (fst it) m)) m.
Definition union_default_val (m : members) := compact_sum_gen (fun it => true) (fun it => default_val (field_type (fst it) m)) m.
Inductive pointer_val : Type :=
| ValidPointer: block -> Ptrofs.int -> pointer_val
| NullPointer.

Lemma PV_eq_dec: forall x y: pointer_val, {x = y} + {x <> y}.