(* Lemma headptr_field_compatible' {cs: compspecs}: forall t p, headptr p -> legal_alignas_type t = true -> legal_cosu_type t = true -> sizeof t < Ptrofs.modulus -> complete_type cenv_cs t = true -> field_compatible t nil p. *)

Lemma data_at__field_at {cs: compspecs}:
forall sh t v p, v = default_val t -> data_at_ sh t p |-- field_at sh t nil v p.