with System;
with Ada.Text_IO;
procedure Russ is

   package P is

      type Parent is synchronized interface;
      function Is_Safe (P : Parent) return Boolean is abstract;
      procedure Set_Safety (P : in out Parent; To : Boolean) is abstract;

      protected type Child (Ceiling : System.Priority)
      with Priority => Ceiling
      is new Parent with
         overriding
         function Is_Safe return Boolean;
         overriding
         procedure Set_Safety (To : Boolean);
      private
         Safety : Boolean := False;
      end Child;

   end P;

   package body P is

      protected body Child is
         function Is_Safe return Boolean is (Safety);
         procedure Set_Safety (To : Boolean) is
         begin
            Safety := To;
         end Set_Safety;
      end Child;

   end P;

   A_Child : P.Child (Ceiling => System.Priority'Last);

begin
   Ada.Text_IO.Put_Line (A_Child.Is_Safe'Img);
   A_Child.Set_Safety (True);
   Ada.Text_IO.Put_Line (A_Child.Is_Safe'Img);
end Russ;