[C++-sig] Boost::Python to_python converter

[DarkAnt]

I'm having a conceptual issue with the way C++ interfaces with Python.
I'm trying to convert a C++ object to a Python object, but my attempt
causes the program to crash. I suspect I'm doing a lot of things
wrong. Ultimately I'd like to be able to pass C++ objects to a python
function that modifies their values.

#include <boost/python.hpp>
#include <string>
struct Unit
{
   int health;
   std::string name;
   std::string type;
   std::pair<int,int> coord;
};

struct Unit_to_python
{
   static PyObject* convert(Unit const& unit)
   {
      return boost::python::incref(boost::python::object(unit).ptr());
   }
};

BOOST_PYTHON_MODULE(game)
{
   boost::python::class_<Unit>("Unit")
      .def_readwrite("health", &Unit::health)
      .def_readwrite("name", &Unit::name)
      .def_readwrite("type", &Unit::type)
      .def_readwrite("coord", &Unit::coord)
   ;
}

int main(int argc, char** argv)
{
   Py_Initialize();
   boost::python::to_python_converter<Unit, Unit_to_python>();
   Unit unit1;
   unit1.health = 100;
   unit1.name = "Tank";
   unit1.type = "Armor";
   boost::python::object foo(unit1); // crash: stack overflow
   return 0;
}