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From: Brad Moore <brad.moore@shaw.ca>
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Subject: Re: newbie: can't read fast enough... :-)    memory leaks...
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Date: 2014-09-04T08:23:50-06:00
List-Id: <comp.lang.ada>

On 2014-09-03 11:32 PM, Jeffrey Carter wrote:
> On 09/03/2014 09:57 PM, Brad Moore wrote:
>>
>>       declare
>>          type String_Access is access String;
>>          A, B : String_Access;
>>       begin
>>          A := new String'("String 1");
>>          B := new String'("String 2");
>>          ... -- Operate on the data.
>>       end;
>>       -- A and B are automatically freed here because the String_Access
>>       -- is finalized since the scope of the declaration of the access
>>       -- type is being exited, and finalizing an access type also
>>       -- finalizes its collection (allocated objects designated by that
>>       -- type).
>>
>> This is a nice way to free up a bunch of objects that are no longer needed, if
>> it can be guaranteed that the objects are only needed in a nested scope. I like
>> this better than garbage collection, because the
>> deallocation occurs more consistently, when and where it is needed.
>> I view this as being less error prone, if one is able to take advantage of this
>> approach.
>
> Recent comments here in another thread indicate that this only works if
> 'Storage_Size is defined for the access type.
>


That doesn't appear to be correct.

In the latest GNAP GPL, the following program outputs;

Finalizing
Finalizing
Exited Block


with Ada.Text_IO; use Ada.Text_IO;
with Ada.Finalization; use Ada;
procedure Test_Deallocation is
begin

    declare
       type T is new Finalization.Limited_Controlled with null record;
       overriding procedure Finalize   (Object : in out T);
       overriding procedure Finalize (Object : in out T) is
       begin
          Put_Line ("Finalizing ");
       end Finalize;

       type T_Access is access T;
       T1, T2 : T_Access;
    begin
       T1 := new T;
       T2 := new T;
    end;

    Put_Line ("Exited Block");

end Test_Deallocation;