vc6.0 mem_fun 无法使用 void func() 的解决办法

#include <boost/smart_ptr.hpp>
#include <functional>

using namespace std;

  // TEMPLATE CLASS mem_fun_void_t
template<class _Ty>
 class mem_fun_void_t : public unary_function<_Ty *, void> {
public:
 explicit mem_fun_void_t(void (_Ty::*_Pm)())
  : _Ptr(_Pm) {}
 void operator()(_Ty *_P) const
  { ((_P->*_Ptr)()); }
private:
 void (_Ty::*_Ptr)();
 };
  // TEMPLATE FUNCTION mem_fun_void
template<class _Ty> inline
 mem_fun_void_t<_Ty> mem_fun_void(void (_Ty::*_Pm)())
 {return (mem_fun_void_t<_Ty>(_Pm)); }

class CA
{
public:
 CA()
 {
 }
 void release()
 {
 }
};

int main(int argc, char* argv[])
{
 boost::shared_ptr< CA > sp(new CA, mem_fun_void(&CA::release));

 return 0;
}