Definition funspec2pre (ext_link: Strings.String.string -> ident) (A : TypeTree)
  (P: forall ts, dependent_type_functor_rec ts (AssertTT A) mpred)
  (ids: list ident) (id: ident) (sig : signature) (ef: external_function) x (ge_s: injective_PTree block)
           (tys : list typ) args (z : Z) m : Prop :=
  match oi_eq_dec (Some (id, sig)) (ef_id_sig ext_link ef) as s
  return ((if s then (rmap* (sigT (fun ts => dependent_type_functor_rec ts A mpred)))%type else ext_spec_type Espec ef) -> Prop)
  with
    | left _ => fun x' => Val.has_type_list args (sig_args (ef_sig ef)) /\
                      exists phi0 phi1, join phi0 phi1 (m_phi m)
                       /\ P (projT1 (snd x')) (projT2 (snd x')) (make_ext_args (filter_genv (symb2genv ge_s)) ids args) phi0
                       /\ necR (fst x') phi1 /\ joins (ghost_of (m_phi m)) (Some (ghost_PCM.ext_ref z, NoneP) :: nil)
    | right n => fun x' => ext_spec_pre Espec ef x' ge_s tys args z m
  end x.Definition funspec2post (ext_link: Strings.String.string -> ident) (A : TypeTree)
  (Q: forall ts, dependent_type_functor_rec ts (AssertTT A) mpred)
  id sig ef x ge_s (tret : option typ) ret (z : Z) m : Prop :=
  match oi_eq_dec (Some (id, sig)) (ef_id_sig ext_link ef) as s
  return ((if s then (rmap*(sigT (fun ts => dependent_type_functor_rec ts A mpred)))%type else ext_spec_type Espec ef) -> Prop)
  with
    | left _ => fun x' => exists phi0 phi1, join phi0 phi1 (m_phi m)
                       /\ Q (projT1 (snd x')) (projT2 (snd x')) (make_ext_rval (filter_genv (symb2genv ge_s)) ret) phi0
                       /\ necR (fst x') phi1 /\ joins (ghost_of (m_phi m)) (Some (ghost_PCM.ext_ref z, NoneP) :: nil)
    | right n => fun x' => ext_spec_post Espec ef x' ge_s tret ret z m
  end x.Definition funspec2extspec (ext_link: Strings.String.string -> ident) (f : (ident*funspec))
  : external_specification juicy_mem external_function Z :=
  match f with
    | (id, mk_funspec ((params, sigret) as fsig) cc A P Q NEP NEQ) =>
      let sig := funsig2signature fsig cc in
      Build_external_specification juicy_mem external_function Z
        (fun ef => if oi_eq_dec (Some (id, sig)) (ef_id_sig ext_link ef) then (rmap* (sigT (fun ts => dependent_type_functor_rec ts A mpred)))%type else ext_spec_type Espec ef)
        (funspec2pre ext_link A P (fst (split params)) id sig)
        (funspec2post ext_link A Q id sig)
        (fun rv z m => False)
  end.

Lemma make_ext_args_symb (ge ge' : genv) (H: Genv.genv_symb ge = Genv.genv_symb ge') n args : make_ext_args (filter_genv ge) n args = make_ext_args (filter_genv ge') n args.