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From: Dmitry A.Kazakov <mailbox@dmitry-kazakov.de>
Newsgroups: comp.lang.ada
Subject: Overriding discriminants perplexes GNAT 3.14p
Date: Thu, 19 Sep 2002 04:32:18 +0200
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Date: 2002-09-19T04:32:18+02:00
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Hi!

The following primitive code causes "GNAT bug detected" report:
--------
with Ada.Finalization; use Ada.Finalization;

package Test1 is
   type X (N : Natural) is
      new Ada.Finalization.Limited_Controlled with private;
   procedure Initialize (Obj : in out X);
private
   type X (N : Natural) is
      new Ada.Finalization.Limited_Controlled with
   record
      NS : String (1..N);
   end record;
end Test1;
----------
package body Test1 is
   procedure Initialize (Obj : in out X) is
   begin
      null;
   end Initialize;
end Test1;
----------
package Test1.Test2 is
   type XX (M : Natural; N : Natural)  is new X with private;
   procedure Initialize (Obj : in out XX);
private
   type XX (M : Natural; N : Natural)  is new X (N) with
   record
      MS : String (1..M);
   end record;
end Test1.Test2;
----------
package body Test1.Test2 is
   procedure Initialize (Obj : in out XX) is
   begin
      Initialize (X (Obj));
   end Initialize;
end Test1.Test2;
----------
package Test1.Test2.Test3 is
   type XXX is new XX (10, 20) with private;
   procedure Initialize (Obj : in out XXX);
private
   type XXX is new XX (10, 20) with null record;
end Test1.Test2.Test3;
----------
package body Test1.Test2.Test3 is
   procedure Initialize (Obj : in out XXX) is
   begin
      Initialize (XX (Obj));
   end Initialize;
end Test1.Test2.Test3;
----------
1. Unconstrained type X has a discriminant
2. Unconstrained XX (derived from X) has two disriminants. It overrides the 
discriminant of X
3. Constrained XXX is derived from XX.

This results in a bug report (crash)  under Windows.

What wonders me is which sort of validation uses ACT if such bugs go 
through? People rightly criticize MS VC++, but the situation with Ada 
compilers isn't much better. I judge from my experience with GNAT and 
Object Ada. It is a permanent battle of finding work-arounds for countless 
compiler bugs. Is there any good Ada compilers since DEC gone?

-- 
Regards,
Dmitry Kazakov
www.dmitry-kazakov.de