Definition field_address t gfs p :=
  if (field_compatible_dec t gfs p)
  then offset_val (nested_field_offset t gfs) p
  else Vundef.Definition field_address0 t gfs p :=
  if (field_compatible0_dec t gfs p)
  then offset_val (nested_field_offset t gfs) p
  else Vundef.

Lemma gfield_type_nested_pred: forall {atom_pred: type -> bool}, atom_pred Tvoid = true -> forall (t: type) (gf: gfield), nested_pred atom_pred t = true -> nested_pred atom_pred (gfield_type t gf) = true.