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,FREEMAIL_FROM
	autolearn=ham autolearn_force=no version=3.4.4
X-Google-Thread: 103376,5f9c25380ec58962
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII
Received: by 10.68.211.195 with SMTP id ne3mr5651152pbc.2.1326646640791;
        Sun, 15 Jan 2012 08:57:20 -0800 (PST)
Path: 
 lh20ni185500pbb.0!nntp.google.com!news1.google.com!postnews.google.com!m4g2000vbc.googlegroups.com!not-for-mail
From: AdaMagica <christ-usch.grein@t-online.de>
Newsgroups: comp.lang.ada
Subject: Re: Elaboration circularity with generics
Date: Sun, 15 Jan 2012 08:55:57 -0800 (PST)
Organization: http://groups.google.com
Message-ID: <3a04e681-8180-4722-9b19-414173073d8e@m4g2000vbc.googlegroups.com>
References: <583b1bfe-95bd-4669-b16b-c733c81e8f88@w4g2000vbc.googlegroups.com>
 <c660cabc-0745-4cd5-a5c9-610767835a50@g27g2000yqa.googlegroups.com>
 <m2sjjhq4vs.fsf@pushface.org>
NNTP-Posting-Host: 91.7.67.241
Mime-Version: 1.0
X-Trace: posting.google.com 1326646640 12763 127.0.0.1 (15 Jan 2012 16:57:20
 GMT)
X-Complaints-To: groups-abuse@google.com
NNTP-Posting-Date: Sun, 15 Jan 2012 16:57:20 +0000 (UTC)
Complaints-To: groups-abuse@google.com
Injection-Info: m4g2000vbc.googlegroups.com; posting-host=91.7.67.241;
 posting-account=rmHyLAoAAADSQmMWJF0a_815Fdd96RDf
User-Agent: G2/1.0
X-Google-Web-Client: true
X-Google-Header-Order: HUALESNKRC
X-HTTP-UserAgent: Mozilla/5.0 (Windows NT 6.0;
 rv:8.0.1) Gecko/20100101 Firefox/8.0.1,gzip(gfe)
Content-Type: text/plain; charset=ISO-8859-1
Content-Transfer-Encoding: quoted-printable
Date: 2012-01-15T08:55:57-08:00
List-Id: <comp.lang.ada>

On 14 Jan., 23:46, Simon Wright <si...@pushface.org> wrote:
> AdaMagica <christ-usch.gr...@t-online.de> writes:
> > A unit can only be instantiated if it is fully elaborated.
> > I guess GNAT chose the elaboration order P'Spec, P.Q'Spec, P'Body
> > (crash since P.Q'body is not elaborated).
> > This dependence is not present for nongeneric units.
>
> > Perhaps addition of pragma Elaborate_Body to P.Q helps.
>
> =A0 =A0with P.Q;
> =A0 =A0pragma Elaborate (P.Q); =A0 =A0 =A0 =A0 =A0<<<<<<< does the trick =
for me
> =A0 =A0package body P is

Of course this works, but in my opinion, Elaborate_Body is better
because it has to be applied just once to P.Q, whereas Elaborate has
to be applied on every unit withing P.Q.

As a general rule of thumb I think Elaborate_Body should be applied
whenever a unit provides functions that are used in the spec of other
units providing initial values or constants, such like:

package P is
  pragma Elaborate_Body;  -- prevents elaboration error when F is
called
  function F (...) return T;
end P;

with P;  -- no need for "pragma Elaborate (P);"
package Q is
  V: [constant] T :=3D P.F (...);
end Q;