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: 103376,46474020a5b291b7
X-Google-Attributes: gid103376,public
X-Google-Language: ENGLISH,ASCII-7-bit
Path: 
 g2news2.google.com!news1.google.com!news4.google.com!border1.nntp.dca.giganews.com!nntp.giganews.com!local01.nntp.dca.giganews.com!nntp.megapath.net!news.megapath.net.POSTED!not-for-mail
NNTP-Posting-Date: Thu, 21 Sep 2006 17:11:49 -0500
From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
References: <1158872883.994303.80430@b28g2000cwb.googlegroups.com>
Subject: Re: Free'ing dynamic abstract tagged types..
Date: Thu, 21 Sep 2006 17:12:09 -0500
X-Priority: 3
X-MSMail-Priority: Normal
X-Newsreader: Microsoft Outlook Express 6.00.2800.1807
X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1807
Message-ID: <uNidneizepC7k47YnZ2dnUVZ_sGdnZ2d@megapath.net>
NNTP-Posting-Host: 64.32.209.38
X-Trace: 
 sv3-LF3oX8QoiSOqJxcuCKSGqBIdGV3YJpfKdX6ent3jXqKpmo7doNso4N+yHgo5ciCgmtdfS+k/9DOgXNC!cKKo6E63Eb6htMJjqzzH5kaPK+VGa04b5XOd2vz6Zyo0fgndT/x3AKTzTRad2AXUGqvooPRgR8kX!pQpI2Re/6SdHVw==
X-Complaints-To: abuse@megapath.net
X-DMCA-Complaints-To: abuse@megapath.net
X-Abuse-and-DMCA-Info: Please be sure to forward a copy of ALL headers
X-Abuse-and-DMCA-Info: Otherwise we will be unable to process your complaint
 properly
X-Postfilter: 1.3.32
Xref: g2news2.google.com comp.lang.ada:6691
Date: 2006-09-21T17:12:09-05:00
List-Id: <comp.lang.ada>

"ldb" <ldb_nospam@hotmail.com> wrote in message
news:1158872883.994303.80430@b28g2000cwb.googlegroups.com...
> Ok, so I have this abstract tagged type called Person (for the sake of
> discussion), and I have an Access_Person (which is access all
> people'class).
>
> I have some derived types, like Man and Child, with their own added
> fields. And I have defined Access_Man, Access_Child, as normal accesses
> to these types.
>
> I want to free an Access_Person that was dynamically allocated.
> ap : Access_Person;
> begin
> ap := Access_Person(new Man);
> free(ap);
> ...
>
> I can't figure out how to write the free routine, since unchecked
> deallocation wants a pointer (presumably access_man), but all I have is
> a class-wide pointer, and I can't figure out how, or if, I can convert
> it. Does that make sense?

No. ;-)

You just free the access and let the compiler take care of it. That is, just
instantiate Unchecked_Deallocation appropriately:

    procedure Person_Free is new Ada.Unchecked_Deallocation (Person'Class,
Access_Person);

and then call it.

> Using free(ap.all), I can make an abstract function that will dispatch
> and free any nested allocations, but I can't seem to get it to free the
> record, itself.

Right, you have to do that on the pointer. You could write something like:

          procedure Free (P :  Access_Person) is
          begin
                 Free (P.all); -- Free the contents
                 Person_Free (P); -- Free the object itself.
          end Free;

but if the derived types need internal clean-up, it's better to make the
whole tree controlled and let the compiler do all of the internal clean-up:
that makes it much harder to forget.

Since you can't add Controlled to an inheritance tree after the fact, I
think that *all* tagged type trees should be derived from Controlled or
Limited_Controlled. (Otherwise, you're saying that the extensions don't need
any clean-up, which is likely to be constraining.)

                                  Randy.