How about this:

#include <vector>

class A
{
private:
std::vector< int > m_vCommon;

public:
A( void ){};
~A( void ){};
std::vector< int >* GetCommonVector Ptr( void )
{
return &m_vCommon;
};
};

class B
{
private:
std::vector< int >* m_pvCommon;

public:...