gcc/testsuite/gnat.dg/protected_null.adb

   1 --  { dg-do compile }
   2
   3 procedure Proc is
   4    protected Po is
   5       procedure P is null;  --  { dg-error " protected operation cannot be a null procedure" }
   6    end Po;
   7    protected body Po is
   8       procedure P is
   9       begin
  10          null;
  11       end P;
  12    end Po;
  13 begin
  14    null;
  15 end;