问 如何使用std::shared_ptr进行boost：：序列化工作？

#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/serialization/shared_ptr.hpp>
#include <fstream>
#include <memory>
#include <vector>
class A
public:
    std::shared_ptr<int> v;
    void A::Save(char * const filename);
    static A * const Load(char * const filename);
        //////////////////////////////////
        // Boost Serialization:
    private:
        friend class boost::serialization::access;
        template<class Archive> void serialize(Archive & ar, const unsigned int file_version) 
            ar & v;
// save the world to a file:
void A::Save(char * const filename)
    // create and open a character archive for output
    std::ofstream ofs(filename);
    // save data to archive
        boost::archive::text_oarchive oa(ofs);
        // write the pointer to file
        oa << this;
// load world from file
A * const A::Load(char * const filename)
    A * a;
    // create and open an archive for input
    std::ifstream ifs(filename);
    boost::archive::text_iarchive ia(ifs);
    // read class pointer from archive
    ia >> a;
    return a;