VMemPool - Virtual Memory Pool Management class

#include <assert.h>
#include <malloc.h>

////////////////////////////////////////////////////////////////////////////////
template<typename T>
class CVIemPool
{
public:
    static int m_dwObjSize;
    void* operator new ( size_t z )
    {
        m_dwObjSize = z;
        return malloc( z );
    }
};

////////////////////////////////////////////////////////////////////////////////
//==============================================================================
class I1 : public CVIemPool<I1> // CVIemPool<I1> is a signature parametered with M1
{
public:
    char m_aGrowing[ 10 ];
};

//==============================================================================
class I2 : virtual public I1
{
public:
    char m_aBulge[ 10 * 10 ];
};

////////////////////////////////////////////////////////////////////////////////
template<typename T> int CVIemPool<T>::m_dwObjSize;

void main()
{
    // The C++'s semantic requemnt. This assert will be successful
    assert ( &(I2::m_dwObjSize) == &I1::m_dwObjSize );

    // The mutable CVIemPool<float>::m_dwObjSize :DDDDDDDDDDDDD

    // this new will change the CVIemPool<float>::m_dwObjSize to sizeof(I1)
    I1* m1 = new I1;
    assert( CVIemPool<I1>::m_dwObjSize == sizeof( I1 ) );

    // this new will change the CVIemPool<float>::m_dwObjSize to sizeof(I2)
    I2* m2 = new I2;
    assert( CVIemPool<I1>::m_dwObjSize == sizeof( I2 ) );

    // But, this assert will fail.
    assert ( sizeof( I2 ) == sizeof( I1 ) );
}

<br />
class CObj: public CVMemPool<br />
{<br />
...<br />
};<br />
<br />
class CGlobObj<br />
{<br />
   CObj * obj;<br />
   CGlobObj()<br />
   {<br />
       obj = new CObj();<br />
   }<br />
};<br />
<br />
<br />
/// this will cause surprise around (CSLock) m_csLock inside the CVMemPool class<br />
/// during "new CObj()" call.<br />
CGlobObj bug;<br />
<br />
int main()<br />
{<br />
 ...<br />
}<br />

VMemPool_demo\VMemPool.h(328) : warning C4346: 'CVMemPool<objT,_dwPoolSizeT>::CSLock': dependent name is not a type
        prefix with 'typename' to indicate a type
VMemPool_demo\VMemPool.h(328) : error C2143:  syntax error : missing ';' before 'CVMemPool<objT,_dwPoolSizeT>::ms_csLock'
VMemPool_demo\VMemPool.h(328) : error C2501: 'CVMemPool<objT,_dwPoolSizeT>::CSLock': missing storage-class or type specifiers

<br />
// A sample where the memory pool is implemented as part of the class.<br />
class CEmployee<br />
{<br />
  // define new / delete to map to m_MemPool new / delete<br />
  // a macro can be defined to automatically do that<br />
  // #define USE_MEM_POOL(class,mempool)<br />
  // in this case USE_MEM_POOL(CEmployee, m_MemPool);<br />
<br />
private:<br />
  static VMemPool<CEmployee> m_MemPool;<br />
}<br />

<br />
// A sample where the memory pool is implemented as part of a collection<br />
// class.<br />
class CMyList<br />
{<br />
  // in this case the list should use m_3rdPartyMemPoolA to new or <br />
  // delete instances of C3rdPartClassA.  In this case it is not<br />
  // as transparent, but it is possible.<br />
<br />
private:<br />
  VMemPool<C3rdPartyClassA> m_3rdPartyMemPoolA;<br />
  VMemPool<C3rdPartyClassB> m_3rdPartyMemPoolB;<br />
}<br />

for( int i = 0 ; i < n; i++)
{
    p[i] = new CVMObj;
    p[i] ->data [0] = 0;
}