From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.4
X-Google-Language: ENGLISH,ASCII-7-bit
X-Google-Thread: 103376,436e4ce138981b82
X-Google-Attributes: gid103376,public
X-Google-ArrivalTime: 2004-03-06 15:20:42 PST
Path: archiver1.google.com!postnews1.google.com!not-for-mail
From: dan@irvine.com (Dan Eilers)
Newsgroups: comp.lang.ada
Subject: Re: abstract sub programs overriding
Date: 6 Mar 2004 15:20:42 -0800
Organization: http://groups.google.com
Message-ID: <aff68d75.0403061520.18593325@posting.google.com>
References: <5f59677c.0403021101.4ac263d0@posting.google.com>
 <mailman.58.1078278195.327.comp.lang.ada@ada-france.org>
 <5f59677c.0403050702.5387352b@posting.google.com>
NNTP-Posting-Host: 67.114.58.28
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: 8bit
X-Trace: posting.google.com 1078615242 17876 127.0.0.1 (6 Mar 2004 23:20:42
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Sat, 6 Mar 2004 23:20:42 +0000 (UTC)
Xref: archiver1.google.com comp.lang.ada:6111
Date: 2004-03-06T15:20:42-08:00
List-Id: <comp.lang.ada>

evangeli@cnam.fr (Evangelista Sami) wrote in message news:<5f59677c.0403050702.5387352b@posting.google.com>...
> here is the code :
>...
> it crashes on "Generate(El.all);" :
> raised CONSTRAINT_ERROR : main.adb:7 access check failed

Here is a slightly modified version.
It still crashes, but commenting out "type unused" makes
it work fine.

procedure Main is
  package Generator is

     type Element_Record is abstract tagged null record;
     type Element is access all Element_Record'Class;

     procedure Generate (El : Element_Record) is abstract;

     type Decl_Record is abstract
        new Element_Record with null record;

     type Type_Decl_Record is new Decl_Record with null record;

     type Discrete_Type_Decl_Record is
        new Type_Decl_Record with private;
     type Discrete_Type_Decl is access all Discrete_Type_Decl_Record;

     procedure Generate (El : Type_Decl_Record);

     type unused is new Discrete_Type_Decl_Record with private;

  private

     type Discrete_Type_Decl_Record is
        new Type_Decl_Record with null record;

     type unused is new Discrete_Type_Decl_Record with null record;

  end Generator;

  package body Generator is
     procedure Generate (El : Type_Decl_Record) is
     begin
        null;
     end;
  end Generator;

  use generator;
  x: Discrete_Type_Decl := new Discrete_Type_Decl_Record;
begin
   Generate(Element(x).all);
end;