提升包装指针的类的序列化

我有一个包含指针的类 Ptr . 该指针可以处理诸如 Ptr<A> 之类的结构，其中 A 可以是复杂的结构或基元，例如 Ptr<double> . 我想指定 Ptr serilaization的 save 和 load 函数来适用于这两种情况 .
在这里，我尝试重现一个简化的例子：

struct A { 
    A(int aa) : a(aa) {} 
    int a; 
    template<class Archive>
    void serialize(Archive &ar, const unsigned int version) {
        ar & BOOST_SERIALIZATION_NVP(a);
    }
};

template <typename T>
struct Ptr {
    Ptr() : m_elem(0) {}
    Ptr(const T* elem) { m_elem = (elem ? new T(*elem) : 0); };
    const T& operator*() const { return *m_elem; };
    T& operator*()  { return *m_elem; };
    const T* operator->() const { return m_elem;};
    T* operator->() { return m_elem;};

    // [...] other ctor, copy, del, etc...

    T* m_elem;
};

namespace boost { namespace serialization {

template<class Archive, class T>
void save(Archive & ar, const Ptr<T> &ptr, const unsigned int version) {
    T* base_pointer = (ptr.m_elem);
    ar & boost::serialization::make_nvp("Ptr", base_pointer);
}

template<class Archive, class T>
void load(Archive & ar, Ptr<T> &ptr, const unsigned int version) {
    T *base_pointer;
    ar & boost::serialization::make_nvp("Ptr", base_pointer);
    ptr.m_elem = base_pointer;
}

template<class Archive, class T>
void serialize(Archive & ar, Ptr<T> &ptr, const unsigned int version)
{
    boost::serialization::split_free(ar, ptr, version);
}

}} // end namespace

int main() {
    Ptr<A> p1(new A(4));
    std::cout << p1.m_elem->a << std::endl;
    Ptr<double> p2(new double(2.0));
    std::cout << *(p2.m_elem) << std::endl;

    // The serialization for Ptr<A> seems to work
    std::ostringstream archive_ostream;
    boost::archive::xml_oarchive oa(archive_ostream);
    oa << BOOST_SERIALIZATION_NVP(p1); 
    std::cout << archive_ostream.str() << std::endl;

    // Serialization for Ptr<double> does not compile
    /*
    std::ostringstream archive_ostream2;
    boost::archive::xml_oarchive oa2(archive_ostream2);
    oa2 << BOOST_SERIALIZATION_NVP(p2); 
    std::cout << archive_ostream2.str() << std::endl;
    */
}

Live example

正如您所看到的， Ptr<A> 的序列化似乎有效（我仍然不确定它是否足够安全） . 但是， Ptr<double> 的序列化未编译 .

错误输出是：

main.cpp：实例化'void boost :: serialization :: save（Archive＆，const Ptr＆，unsigned int）[with Archive = boost :: archive :: xml_oarchive; T = A]'：/ usr / local /include/boost/serialization/split_free.hpp:45:13：需要'static void boost :: serialization :: free_saver :: invoke（Archive＆，const T＆，unsigned int）[与Archive = boost :: archive :: xml_oarchive; T = Ptr]'/usr/local/include/boost/serialization/split_free.hpp:74:18：需要'void boost :: serialization :: split_free（Archive＆，T＆，unsigned int）[with Archive = boost ::存档:: xml_oarchive; T = Ptr]'main.cpp：57：34：需要'void boost :: serialization :: serialize（Archive＆，Ptr＆，unsigned int）[with Archive = boost :: archive :: xml_oarchive; T = A]'

因此，我正在寻找一个正确的 Ptr 序列化！