gnat: Execution_Time is not supported in this configuration

[singo <sander.ingo@gmail.com>]

Dear Ada community,

I have recently become very interested of Ada 2005, and it's real-time
annex. However, as a new user of Ada I face some problems with the
software.

I cannot get the package Ada.Execution_Time to work with gnat,
although the gnat documentation says that the real-time annex is fully
supported... I use the gnat version 4.4 on a Ubuntu 9.10 distribution.

The typical error message I get is

gcc -c executiontime.adb
Execution_Time is not supported in this configuration
compilation abandoned

How can I configure gnat to support the Ada.Execution_Time package?

Hopefully somebody can help me!

Thanks in advance!

Ingo

Below follows an example program that generates the error messge.

with Ada.Text_IO; use Ada.Text_IO;
with Ada.Real_Time; use Ada.Real_Time;
with Ada.Execution_Time;

procedure ExecutionTime is
   task T;

   task body T is
      Start : CPU_Time;
      Interval : Time_Span := Milliseconds(100);
   begin
      Start := Ada.Execution_Time.Clock;
      loop
         Put_Line(Duration'Image(Ada.Execution_Time.Clock - Start));
         delay To_Duration(Interval);
      end loop;
   end T;
begin
   null;
end ExecutionTime;