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-Thread: 103376,5f0f4bfb0467bb19
X-Google-NewGroupId: yes
X-Google-Attributes: gida07f3367d7,domainid0,public,usenet
X-Google-Language: ENGLISH,ASCII-7-bit
Received: by 10.68.73.233 with SMTP id o9mr1516809pbv.8.1320829209963;
        Wed, 09 Nov 2011 01:00:09 -0800 (PST)
Path: 
 h5ni15884pba.0!nntp.google.com!news2.google.com!goblin1!goblin.stu.neva.ru!eternal-september.org!feeder.eternal-september.org!.POSTED!not-for-mail
From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Constructors with multiple inheritance
Date: Wed, 09 Nov 2011 09:00:03 +0000
Organization: A noiseless patient Spider
Message-ID: <m2obwlbrho.fsf@pushface.org>
References: 
 <11513972.2788.1317325228383.JavaMail.geo-discussion-forums@yqnv12>
	<1rj1mmkvwud1d.dzqoy4jhdfca$.dlg@40tude.net>
	<4976045.4489.1317352313370.JavaMail.geo-discussion-forums@yqjw35>
	<2pu3h5hqltxi$.ze4yrf1f2y8z.dlg@40tude.net>
	<23774546.1654.1317391464047.JavaMail.geo-discussion-forums@yqnk41>
	<1gnrks1djlaok.1k0r5f8z9ylfx.dlg@40tude.net>
	<21605158.153.1320805494018.JavaMail.geo-discussion-forums@yqiu15>
Mime-Version: 1.0
Injection-Info: mx04.eternal-september.org;
 posting-host="dFCm8HWntFqmDIilBLqEJQ";
	logging-data="9977"; mail-complaints-to="abuse@eternal-september.org";
	posting-account="U2FsdGVkX19I6onJrEPOF03JCGg47pliNY9BRTFh3sM="
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.3 (darwin)
Cancel-Lock: sha1:6rMu/xcSC9Zefaa+FTaXy4IcaZI=
	sha1:8dXHgx6Cx3Ldr61y2LyVf06ejOE=
Xref: news2.google.com comp.lang.ada:14366
Content-Type: text/plain; charset=us-ascii
Date: 2011-11-09T09:00:03+00:00
List-Id: <comp.lang.ada>

"Rego, P." <pvrego@gmail.com> writes:

>     procedure Test_Pkg_User is
>        Test_Obj : Test_Pkg.Test_Class_Ptr;
>     begin
>        Test_Obj := Test_Obj.Construct;
>        Put_Line ("Value = "&Integer'Image (Test_Obj.Info));
>     end Test_Pkg_User;
>
> The message I get is the following:
>     c:\tst>gnatmake test_pkg_user.adb
>     gcc -c test_pkg_rev623_user.adb
>     test_pkg_user.adb:12:16: warning: null value not allowed here
>     test_pkg_user.adb:12:16: warning: "Constraint_Error" will be raised at run time
>     gcc -c test_pkg.adb
>     gnatbind -x test_pkg_user.ali
>     gnatlink test_pkg_user.ali
>
> What am I still doing wrong? Thanks again.
>
> Note: Sure if I put in test_pkg_user.adb
>     Test_Obj : Test_Pkg.Test_Class_Ptr := new Test_Pkg.Test_Class;
> it returns me a build with no warning, but I think this way I allocate
> memory twice to the pointer (one in the call new Test_Pkg.Test_Class
> and the other in the construct method execution), right?

The declaration

   function Construct (T : access Test_Class) return Test_Class_Ptr;

requires T not to be null because of ARM2005 3.10(13.1/2) [1]

   "In addition, the anonymous access subtype defined by the
   access_definition for a controlling access parameter (see 3.9.2)
   excludes null."

Of course, as your code stands, even if you changed Construct to

   function Construct (T : Test_Class_Ptr) return Test_Class_Ptr;

the call would fail anyway because you don't check for T being null
before saying

      T_Ptr.Info := T.Info + 1;

[1] http://www.adaic.org/resources/add_content/standards/05rm/html/RM-3-10.html