Ltac process_stackframe_of :=
 match goal with |- semax _ (_ * stackframe_of ?F) _ _ =>
   let sf := fresh "sf" in set (sf:= stackframe_of F) at 1;
     unfold stackframe_of in sf; simpl map in sf; subst sf
  end;
 repeat
   match goal with |- semax _ (_ * fold_right sepcon emp (var_block _ (?i,_) :: _)) _ _ =>
     match goal with
     | n: name i |- _ => simple apply var_block_lvar2;
       [ reflexivity | reflexivity | reflexivity | reflexivity | clear n; intro n ]
     | |- _ =>    simple apply var_block_lvar2;
       [ reflexivity | reflexivity | reflexivity | reflexivity | let n := fresh "v" i in intros n ]
     end
   end;
 (*
  match goal with |- semax _ ?Pre _ _ =>
     let p := fresh "p" in set (p := Pre);
     rewrite <- (@emp_sepcon (environ->mpred) _ _ _ (fold_right _ _ _));
     subst p
  end;
  repeat (simple apply postcondition_var_block;
   [reflexivity | reflexivity | reflexivity | reflexivity | reflexivity |  ]);
*)
 change (fold_right sepcon emp (@nil (environ->mpred))) with
   (@emp (environ->mpred) _ _);
 rewrite ?sepcon_emp, ?emp_sepcon.Definition tc_option_val' (t: type) : option val -> Prop :=
 match t with Tvoid => fun v => match v with None => True | _ => False end | _ => fun v => tc_val t (force_val v) end.

Lemma tc_option_val'_eq: tc_option_val = tc_option_val'.