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From: Marius Amado Alves <amado.alves@netcabo.pt>
Newsgroups: comp.lang.ada
Subject: Re: Memory leak - What the ...?
Date: Tue, 12 Oct 2004 17:05:42 +0100
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Date: 2004-10-12T17:05:42+01:00

>>I still lack an understandable explanation of why this does not leak:
>>
>>       if This.Data /= null then
>>          This.Data := new Stream_Element_Array'(This.Data.all);
>>       end if;
> 
> Adjust is called just after the members of the record have been
> copied. So imagine you have
> 
> A := B;
> 
> When Adjust(A) gets called, you will have
> 
> A.Data = B.Data
> 
> Since Data is an access type, you have a shallow copy where both A and
> B have members pointing to the same heap space.
> 
> In the Adjust, what A does is replicate the pointed data to get a new
> pointer and a deep copy where A and B point to different heap copies.
> 
> Additionally, before A being overwritten, Finalize(A) is called just
> in case it needs to free some memory.
> 
> Hope this helps.

Not really. The only way for leaking not to take place is for the old 
This.Data value being held somewhere. Where? Or for Finalize (A) to be 
called before Adjust, but then This.Data should become null, no? And 
then the if condition would never hold. The alternative being This.Data 
pointing to garbage.