Re: memory leak detection techniques

"David Webber" <>
Wed, 10 Oct 2007 21:37:33 +0100
"Norbert Unterberg" <nunterberg@newsgroups.nospam> wrote in message

How do you know about the leak? Do you see the memory leak dump in the
output window when your application exits?


If yes then you have a good chance. You can set a memory breakpoint on the
allocation ID that is listed in the memory leaks dump. Add a call to
_CrtSetBreakAlloc(<put the ID here>); at the beginning of main()

Thank you! I have never needed that before. I now know where the leak
is, but not why.

But the plot thickens:

In my non-MFC DLL I have a global instance of an object of the form

CMyCollection : public std::vector<CMyThing>;

Its normal constructor is called on startup, which just creates and empty
It is only called once.
It is filled in (also once) with a method of CMyColllection schematically of
the form


    CMyThing thing;

    for( allthings )
        thing = .... // fill in the thing
        push_back( thing ); //*********

It is usually not changed, and lasts until the program shuts down.
It is never copied. (It has a copy constructor, because I feel nervous
without them, but it is never called.)
The destructor is called once, and just calls clear() (because I feel it
is neat to do so).

I am being told that the memory leak is associated with the CMyThing's copy
constructor invoked by push_back() above.

How can that be?

Even stranger, I have had all of this present in the code for years and a
memory leak has only been reported recently.

Any ideas gratefully received.

David Webber
Author of 'Mozart the Music Processor'
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