[boost] seiralization of shared_ptr

19 May 2004

      Some time ago the question was raised on this list as to why it was
necessary to access share_count in order to implement serialization of
shared_ptr.  At the time I didn't have an answer.

So I went back and tried to re-implement it and have come to the following
point beyond which I can't proceed without manipulating shared_count
directly.

/////////////////////////////////////////////////////////////
// implement serialization for shared_ptr<T>

template<class Archive, class T>
inline void save(
    Archive & ar,
    const shared_ptr<T> & t,
    const unsigned int /* file_version */
){
    ar << boost::serialization::make_nvp("px", t.get());
}
template<class Archive, class T>
inline void load(
    Archive & ar,
    shared_ptr<T> & t,
    const unsigned int /* file_version */
){
    // object tracking guarantees that pointers are not replicated
    // on loading.
    T * t_new;
    ar >> boost::serialization::make_nvp("px", t_new);
    // if its not the first time, it should be equal to the current pointer
    assert(0 == t.use_count() || t.get() == t_new);
    // assign new pointer or bump reference count as appropriate
    // ???? - what goes here?
}

Can anybody tell me "what goes here?"

Robert Ramey