How serialize a class with pointer in boost.serialization?

Question

I am trying to serialize a singleton class with pointer.

boost.serialization is a good tools. it can work well if there is no pointer member variable.

once include pointer, read it back will crased.

here is my code:

#include <fstream>
#include <iostream>
#include <boost/archive/text_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/serialization/vector.hpp>
#include <boost/serialization/unordered_map.hpp>
using namespace std;

class gps_position {
 private:
  friend class boost::serialization::access;
  template<class Archive>
  void serialize(Archive & ar, const unsigned int version) {
    ar & degrees;
    ar & minutes;
    ar & seconds;
    ar & v;
    ar & mm; 
  }
  int degrees;
  int minutes;
  float seconds;
  std::vector<double> v;
  std::unordered_map<std::string, std::unordered_map<std::string, double>> mm; 
  std::unordered_map<int, int*> test;  // here stores pointers. if without it, can work well
 private:
  gps_position(){};
  gps_position(int d, int m, float s, double a, double b, double c) : degrees(d), minutes(m), seconds(s) {
    v.push_back(a);
    v.push_back(b);
    v.push_back(c);
    mm["a"]["a"] = c;
    int* aa = new int(3);
    test[1] = aa; 
  }
 public:
  static gps_position& Inst(int d, int m, float s, double a, double b, double c) { static gps_position g(d, m, s, a,b,c); return g;} 
  static gps_position& Inst() { static gps_position g; return g;}
    void print() const {
    std::cout << degrees << " " << seconds << endl;
    cout << "start vector:";
    for (const auto & i : v) cout << i << endl;
    cout << "end vector\n";
    for (auto & i : mm) cout << i.first << "=" << i.second.at("a") << endl;
    cout << "test[1] = " << *(test.at(1)) << endl;
  }
};
void write() {
  std::ofstream ofs("a");
  const gps_position& g = gps_position::Inst(35, 59, 24.567f, 1.2, 3.6, 9.1);
  boost::archive::text_oarchive oa(ofs);
  g.print();
  oa << g;
}

void read() {
  std::ifstream ifs("a");
  boost::archive::text_iarchive ia(ifs);
  gps_position& g = gps_position::Inst();
  ia >> g;
  g.print();  // crashed because print failed in pointer.
}

int main() {
  write();
  read();
}

could you help me on this? how to serialize a class with pointer member variable?