HOWTO resolve circular references in ns-3 memory disposal

HOWTO resolve smart pointer circular references in ns-3 memory disposal

    class A : public Object
    {
    public:
       static TypeId GetTypeId (void);
       void CallbackMethodA();
       Callback<void> m_callback;
    };
    class B : public Object
    {
    public:
       static TypeId GetTypeId (void);
       void CallbackMethodB();
       Callback<void> m_callback;
    };

    int main(int argc, char* argv[])
    {
       Ptr<A> a = CreateObject<A>();
       Ptr'' b = CreateObject();
       a->m_callback = MakeCallback (&B::CallbackMethodB, b);
       b->m_callback = MakeCallback (&A::CallbackMethodA, a);
    }

or

    int main(int argc, char* argv[])
    {
       Ptr<A> a = CreateObject<A>();
       Ptr b = CreateObject();
       a->m_callback = MakeCallback (&B::CallbackMethodB, b);
       b->AggregateObject(a);
    }

    ==15749== LEAK SUMMARY:
    ==15749==    definitely lost: 40 bytes in 1 blocks
    ==15749==    indirectly lost: 152 bytes in 5 blocks
    ==15749==    possibly lost: 0 bytes in 0 blocks
    ==15749==    still reachable: 10,360 bytes in 5 blocks
    ==15749==    suppressed: 0 bytes in 0 blocks