obj.cpp

#include <iostream>

class my_class
{
public:
  void test()
  {
    std::cout << "Hello C++" << std::endl;
  }

  void set_x(double x)
  {
    _x = x;
  }

  double get_x() const
  {
    return _x;
  }

private:
  double _x;
};

template<class T>
class wrapper
{
public:
  template<class R, class... As>
  R call(R(T::*fnp)(As...), As... args)
  {
    return (reinterpret_cast<T*>(this)->*fnp)(std::forward<As>(args)...);
  }

  template<class R, class... As>
  R call(unsigned long addr, As... args)
  {
    union {
      unsigned long u_ul;
      void *u_voidp;
      R(T::*u_mfnp)(As...);
    } call_addr;
    
    call_addr.u_ul = addr;
    return call<R, As...>(call_addr.u_mfnp, std::forward<As>(args)...);
  }
};



int main()
{
  wrapper<my_class> *object = reinterpret_cast<wrapper<my_class>*>(new my_class);

  object->call(&my_class::test);
  
  std::cout << "&my_class::test = " << std::showbase << std::hex << (void*)(&my_class::test) << std::endl
    << "&my_class::set_x = " << std::showbase << std::hex << (void*)(&my_class::set_x) << std::endl
    << "&my_class::get_x = " << std::showbase << std::hex << (void*)(&my_class::get_x) << std::endl
    << std::endl;

  object->call<void>(0x400cce); // test

  object->call<void, double>(0x400cfa, 42.1337); // set

  std::cout << "object->get_x() = " << object->call<double>(0x400d18) << std::endl; // get
}