Valid use of shared_ptr?

Is the following a valid use of shared_ptr?

What I want to do is to be able to create a class on the heap or on the
stack using shared_ptr, but also to be able to get a shared_ptr to it
irrespective of whether it is on the stack or heap.
The following seems to work, if USE_DUMMY_SHARED_POINTER is defined,
but is it correct?

regards
Andy Little

//--------------

#include <iostream>
#include <boost/shared_ptr.hpp>
#include <boost/enable_shared_from_this.hpp>

// MSVC specific stuff to check memory leaks
#if defined (_MSC_VER) && defined(_DEBUG)
#include <crtdbg.h>
#endif
namespace std_tr1 = boost;
struct null_deleter
{
   void operator()(void const*) const
   {
   }
};

// if defined puts a dummy shared_ptr in the class
#define USE_DUMMY_SHARED_POINTER

// class where I want to be able
// to get a shared_pointer to it
// via get_ptr function
struct my : std_tr1::enable_shared_from_this<my>
{
   typedef std_tr1::shared_ptr<my> ptr;
#ifdef USE_DUMMY_SHARED_POINTER
   ptr dummy_shared_ptr;
#endif
   my(){
#ifdef USE_DUMMY_SHARED_POINTER
      ptr temp(this,null_deleter());
      dummy_shared_ptr = temp;
#endif
   }

   ptr get_ptr()
   {
      return shared_from_this();
   }
};

int main()
{
try{
   // try stack alloc
   my x;

   my::ptr px = x.get_ptr();

   if( px.get() == &x){
      std::cout << "ptr to x checks ok\n";
   }
   else {
      std::cout << "ptr to x bad\n";
   }

  // try heap alloc under shared_ptr management
   my::ptr x_ptr = my::ptr(new my());

   my::ptr px_ptr = x_ptr->get_ptr();

   if( px_ptr == x_ptr){
      std::cout << "ptr to x_ptr checks ok\n";
   }
   else {
      std::cout << "ptr to x_ptr bad\n";
   }

   // try raw alloc
   my* raw_pointer = new my();

   my::ptr raw_ptr = raw_pointer->get_ptr();
   if( raw_pointer == raw_ptr.get()){
      std::cout << "ptr to raw_ptr checks ok\n";
   }
   else {
      std::cout << "ptr to raw_ptr bad\n";
   }
   delete raw_pointer;

   std::cout << "no exceptions\n";
}
catch (std::exception & e){
   std::cout << e.what() <<'\n';
}

//msvc leak checks
  #if defined (_MSC_VER) && defined(_DEBUG)
#define SET_CRT_DEBUG_FIELD(a) \
_CrtSetDbgFlag((a) | _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG))
#define CLEAR_CRT_DEBUG_FIELD(a)\
_CrtSetDbgFlag(~(a) & _CrtSetDbgFlag(_CRTDBG_REPORT_FLAG))

   SET_CRT_DEBUG_FIELD( _CRTDBG_LEAK_CHECK_DF );
#endif

}

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