#include <fstream>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>

/////////////////////////////////////////// Singleton class
class C {
  int x,y,z;
  
  C() : x(1),y(2),z(3) {}

  friend class boost::serialization::access;
  template <typename A>
  void serialize(A &a,unsigned v) { a & x & y & z; }

  //public: //<-- won't compile unless this is public
  ~C() {}

public:
  static C & Instance() {
    static C c;
    return c;
  }
};

/////////////////////////////////////////////////////////////
int main() {
  // create and open a character archive for output
  std::ofstream ofs("filename");

  boost::archive::text_oarchive oa(ofs);
  oa << C::Instance();
}