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From: Simon Wright <simon@pushface.org>
Newsgroups: comp.lang.ada
Subject: Re: Deallocating list of polymorphic objects?
Date: Fri, 01 Dec 2006 06:41:44 +0000
Organization: Pushface
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Date: 2006-12-01T06:41:44+00:00
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Robert A Duff <bobduff@shell01.TheWorld.com> writes:

> But, to be safe, you should ensure that the result type of each
> "new" is the same as the type passed to Unchecked_Deallocation.

In the Ada95 context I've come across this most (a procedure takes
access-to-classwide, callers allocate locally) I started off thinking
of something like

  type Bar is tagged private;
  type Bar_P is access Bar'Class;
  type Foo is new Bar with private;
  type Foo_P is access Foo;
  ...
  F : Foo_P := new Foo'(...);
  BC : Bar_P := F.all'Access;
  ...
  Free (BC);

but remembering Bill Taylor's remarks about splattering your code with
".all'Access", and so as to avoid declarations like Foo_P, ended up
with

  type Bar is tagged private;
  type Bar_P is access Bar'Class;
  type Foo is new Bar with private;
  ...
  BC : Bar_P := new Foo'(...);
  F : Foo renames Foo (BC.all);
  ...
  Free (BC);