Re: Memory leak - What the ...?

["Björn Persson" <spam-away@nowhere.nil>]

Marius Amado Alves wrote:

>> 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?

In B, where it's been all the time. If B was a variable on the stack, 
it's still there on the stack, and still points to the old copy of the 
data. If B was itself on the heap, then obviously there's a pointer to B 
somewhere, since it could be accessed and copied to A. That pointer is 
still there, and still points to B, which in turn still points to the 
old copy of the data. If B was a temporary object, then the compiler is 
smart enough to finalize it after A has been adjusted (or else the 
compiler is broken).

-- 
Björn Persson                              PGP key A88682FD
                    omb jor ers @sv ge.
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