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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Question about OO programming in Ada
Date: Wed, 3 Dec 2003 14:05:52 -0600
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Date: 2003-12-03T14:05:52-06:00
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"Hyman Rosen" <hyrosen@mail.com> wrote in message
news:1070466281.168920@master.nyc.kbcfp.com...
> Dmitry A. Kazakov wrote:
> > Of course one could call Unchecked_Deallocation from Finalize
>
> I understand that Ada permits Finalize to be called multiple times
> for an object, so calling Unchecked_Deallocation from Finalize sounds
> like a recipe for disaster.

Finalize should handle tasks for the components, not the object itself. So,
it is possible (and common) to call U_D on components of the object
(presuming that you have a way to check that it hasn't already been done, a
requirement of all Finalize routines). But you never do memory allocation on
the top-level object.

This is precisely how Janus/Ada manages complex objects at runtime, so the
technique is so familar to me I always find it surprising that it is not
obvious to others. Leaving allocation of the object itself to it's owner is
necessary in any case: the object may not even have been allocated on the
heap, or may be a component of some other object.

If you want to manage an access value in Ada 95, you wrap it in a controlled
record type and then you can do the allocation/deallocation safely.

                Randy.