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From: Robert A Duff <bobduff@shell01.TheWorld.com>
Newsgroups: comp.lang.ada
Subject: Re: Heap Memory Management Question(s)
Date: 05 Apr 2006 17:42:09 -0400
Organization: The World Public Access UNIX, Brookline, MA
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Date: 2006-04-05T17:42:09-04:00
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Florian Liekweg <liekweg@gmx.de> writes:

> Sorry for being unclear.  I was thinking of, e.g., a package variable,
> which, as I understand, is not visible and/or accessible everywhere,
> but it exists and keeps its state over the lifetime of the program.
> 
> My assumption is the following:
>    We can momentarily leave the area where the variable is /visible/,
>    but it stays in existence.  The lifetime of the object it points to
>    can now span the entire program, not just the time the variable is
>    visible.
> My conclusion is: Visibility of the access type doesn't help when it
>    comes to determining the lifetime of that object.  NB, it could
>    of course /improve/ whatever analysis a sophisticated compiler
>    might do.

That's correct.  Lifetime is different from visibility.
If you declare:

    X: Integer;

in a library package, it lasts essentially "forever".
Likewise, if you declare an access type:

    type A is access ...;

the heap-allocated objects in A's "collection" can last "forever"
(or you can use Unchecked_Deallocation to destroy them).

- Bob