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From: Samuel Tardieu <sam@ada.eu.org>
Subject: Re: Freeing Pointers to classwide types
Date: 1998/09/25
Message-ID: <87k92sa1kr.fsf@zaphod.enst.fr>#1/1
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Date: 1998-09-25T00:00:00+00:00
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>>>>> "Bob" == Bob Fletcher <fletcherr@logica.com> writes:

Bob> Really? Isn't the object that is created by the 'new' keyword
Bob> similar in nature to a C++ 'heap' variable, in that although the
Bob> pointer may go out of scope the object will not, and needs to be
Bob> explicitly destroyed?

In this case, the pointer *type* goes out of scope, so unless your
object is a task or unless you're using Unchecked_Conversion to
another pointer type (or whatever), your objet (which is passive if it 
isn't a task) is not going to be accessed anymore (you can't affect it 
to an outer access type since it will have a smallest accessibility level).

Example:

| procedure Q is
| 
|    type String_Ptr_Almost_Global is access all String;
| 
|    T : String_Ptr_Almost_Global;
| 
| begin
|    declare
| 	type String_Ptr_Local is access all String;
| 	S : String_Ptr_Local;
|    begin
| 	S := new String'("abcde");
| 	T := String_Ptr_Almost_Global (S);
|    end;
| end Q;

Compiling this with GNAT will lead to:

    13.       T := String_Ptr_Almost_Global (S);
                                             |
        >>> cannot convert local pointer to non-local access type

  Sam
-- 
Samuel Tardieu -- sam@ada.eu.org