pointer to members arithmetic

Hi to all,

to make it short: I'm trying to build a small class that I conditionally
include in some other class just for debugging purposes.
This class should register itself in a container on construction and
unregister on destruction. The point is that I would like to query
the **enclosing class** (just during debugging...) through the
container. (check the code, hope it's clearer than the explanation..)
:-)
  I would like to know if the pointer arithmetics and castings I've used
may bring to "undefined behavior" according to the standard.
I tried to understand it myself but I guess my English is not good
enough... ;-)
Just for the record: I'm trying to follow this path because I do not
want to litter the constructors of the enclosing classes...
Deep regards,
Francesco

P.S.
First posting with Thunderbird... hope it works....

#include <iostream>
#include <set>
#include <algorithm>
#include <functional>

class CDebugBase
{
public:
    static void DumpStatic()
    { std::for_each( sSet.begin(), sSet.end(),
        std::mem_fun( &CDebugBase::Dump ) ); }

protected:

    virtual ~CDebugBase() {}

    virtual void Dump() const = 0;

    static std::set< CDebugBase * > sSet;
};

std::set< CDebugBase * > CDebugBase::sSet;

//

template< typename T >
class CDebug : private CDebugBase
{
public:

    CDebug() { sSet.insert( this ); }
    ~CDebug() { sSet.erase( this ); }

    T const * GetEnclPtr( void ) const
    {
        CDebug< T > T::* membPtr( &T::mDebugObject );
        // IS IT OK?
        return reinterpret_cast< T const * >
        ( this - &( static_cast< T const * >( 0 )->*membPtr ) );
    }

    void Dump() const
    { std::cout << GetEnclPtr() << " - "
        << typeid( T ).name() << '\n'; }

};

//

struct A
{
    CDebug< A > mDebugObject;
};

struct B
{
    CDebug< B > mDebugObject;
};

struct Trigger
{
    ~Trigger( void )
    { std::cout << "-----\n";
        CDebugBase::DumpStatic(); }
} trigger;

//

int main()
{
    A obj1, obj2, obj3;
    B obj4, obj5, obj6;
    A * ptr1 = new A[ 5 ];
    B * ptr2 = new B[ 5 ];
    CDebugBase::DumpStatic();
    std::cout << "--------\n";
    delete[] ptr1;
    delete[] ptr2;
    CDebugBase::DumpStatic();
    std::cout << "--------\n";

}