Re: Self deleting class

"Alex Blekhman" <>
Wed, 24 Oct 2007 21:46:02 +0200
"Lisa Pearlson" wrote:

can I then simply do this?

CSomeClass* c = NULL;

c = new CSomeClass();
c = new CSomeClass();

What happens when I reassign the valiable to new instance?
Will CSomeClass self-delete itself at that point, or when
application terminates?

Other already answered that you'll get memory leak. It is
because pointer `c' knows nothing about about class'
destructor. Pointer just holds an address to the allocated
memory, that's all.

What you need here is so called "smart pointer". Smart
pointer is a class that wraps raw pointer and ensures the
release of acquired resources. You can implement such smart
pointer class by yourself, for example:

class CSomeClassPtr
    CSomeClassPtr(CSomeClass* p = NULL) : m_p(p) {}
    ~CSomeClassPtr() { delete m_p; }

    CSomeClass* operator ->()
    { return m_p; }

    const CSomeClass* operator ->() const
    { return m_p; }

    CSomeClass* operator =(CSomeClass* p)
        if(p != m_p)
            delete m_p;
            m_p = p;

        return m_p;

    CSomeClass* m_p;

Then you can use `CSomeClassPtr' instead of raw pointer:

CSomeClassPtr ptr;

ptr = new CSomeClass();
ptr = new CSomeClass();

However, there is similar smart pointer already implemented
in STL - `std::auto_ptr':

typedef std::auto_ptr<CSomeClass> CSomeClassPtr;

CSomeClassPtr p1(new CSomeClass);
CSomeClassPtr p2(new CSomeClass);


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