Definition cl_halted (c: CC_core) : option val := None.Definition empty_function : function := mkfunction Tvoid cc_default nil nil nil Sskip.Fixpoint temp_bindings (i: positive) (vl: list val) :=
 match vl with
 | nil => PTree.empty val
 | v::vl' => PTree.set i v (temp_bindings (i+1)%positive vl')
 end.Fixpoint params_of_types (i: positive) (l : list type) : list (ident * type) :=
  match l with
  | nil => nil
  | t :: l => (i, t) :: params_of_types (i+1)%positive l
  end.Fixpoint typelist2list (tl: typelist) : list type :=
  match tl with
  | Tcons t r => t::typelist2list r
  | Tnil => nil
  end.Definition params_of_fundef (f: fundef) : list type :=
  match f with
  | Internal {| fn_params := fn_params |} => map snd fn_params
  | External _ t _ _ => typelist2list t
  end.Definition cl_initial_core (ge: genv) (v: val) (args: list val) : option CC_core :=
  match v with
    Vptr b i =>
    if Ptrofs.eq_dec i Ptrofs.zero then
      match Genv.find_funct_ptr ge b with
        Some f =>
        Some (CC_core_State empty_function 
                    (Scall None
                                 (Etempvar 1%positive (type_of_fundef f))
                                 (map (fun x => Etempvar (fst x) (snd x))
                                      (params_of_types 2%positive
                                                       (params_of_fundef f))))
                     (Kseq (Sloop Sskip Sskip) Kstop)
             empty_env
             (temp_bindings 1%positive (v::args)))
      | _ => None end
    else None
  | _ => None
  end.Definition stuck_signature : signature := mksignature nil None cc_default.Definition cl_at_external (c: CC_core) : option (external_function * list val) :=
  match c with
  | CC_core_Callstate (External ef _ _ _) args _ => Some (ef, args)
  | CC_core_State _ (Sbuiltin _ ef _ args) _ _ _ => Some (EF_external "stuck" stuck_signature, nil)
  | _ => None
end.Definition cl_after_external (vret: option val) (c: CC_core) : option CC_core :=
   match c with
   | CC_core_Callstate (External ef _ _ _) _ k => 
        Some (CC_core_Returnstate (match vret with Some v => v | _ => Vundef end) k)
   | _ => None
   end.Definition cl_step ge (q: CC_core) (m: mem) (q': CC_core) (m': mem) : Prop :=
    cl_at_external q = None /\ 
     Clight.step ge (Clight.function_entry2 ge)
      (CC_core_to_CC_state q m) Events.E0 (CC_core_to_CC_state q' m').

Lemma cl_corestep_not_at_external: forall ge m q m' q', cl_step ge q m q' m' -> cl_at_external q = None.