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From: "Randy Brukardt" <randy@rrsoftware.com>
Newsgroups: comp.lang.ada
Subject: Re: Weird controlled behavior - Gnat 3.15p NT
Date: Thu, 4 Sep 2003 23:04:34 -0500
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Date: 2003-09-04T23:04:34-05:00
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"Robert I. Eachus" <rieachus@attbi.com> wrote in message
news:3F57B071.5030206@attbi.com...
> Jano wrote:
>
> > Now, I would assume that no Finalization could happen without a
> > corresponding Initialization, so is this normal? Is something wrong in
> > that read way?
>
> No object can be finalized that has not been initialized (or created as
> part of an assignment with adjust)...

No, that's not right either.
Finalizable objects can be "initialized" three ways:
    -- Default initialization followed by a call to Initialize.
    -- Explicit initialization followed by a call to Adjust.
    -- Aggregate initialization.

Note that the latter doesn't call anything. Also note that an abstraction
can make the last illegal by declaring the type as a private type.

In this case, it looks like GNAT is assigning temporaries, so there is a bit
copy, followed by an Adjust call, and then a Finalize call for the
temporary. That accounts for the "extra" calls. For a non-limited controlled
type, you have to account for all three routines; they can get used
implicitly even if you never wrote any assignments.

Finally, Robert's basic point is correct: Finalize should always be designed
to be called "extra" times on an object. I usually use something like:

    procedure Finalize (Obj : in out Object_Type) is
    begin
        if Obj.Inited then
            -- Finalize code.
            Obj.Inited := False;
        -- else not Initialized or already Finalized.
        end if;
    end Finalize;

with Initialize setting the Initted flag. (Often, I use some data in the
record for this purpose, rather than a dedicated flag; such as an allocated
block of memory [if the pointer is null, the object is already Finalized].)

                  Randy.