[boost] [serialization] cyclic references

From: FATH Francois (francois.fath-renexter_at_[hidden])
Date: 2004-05-07 04:24:16

I have difficulties when serializing two objects pointing to each other. 
The generated archive is fine (I can see both references in it), but 
when deserializing, only one is restored. In the attached example, I 
have a collection of nodes, each one is pointing to the previous and to 
the next node. When deserializing, only the ->next references are 
restored, all the ->previous are NULL.

The compiler is VC7.1

Thanks,
Francois Fath

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#include "stdafx.h"
#include <fstream>
#include <boost/archive/xml_oarchive.hpp>
#include <boost/archive/xml_iarchive.hpp>

using namespace std;

class Node
{
public:
        Node(Node *previous = NULL, Node *next = NULL)
        {
                id = ++count;

                this->previous = previous;
                if (previous) previous->next = this;
                this->next = next;
                if (next) next->previous = this;
        }

        ~Node()
        {
                if (previous) previous->next = next;
                if (next) next->previous = previous;
        }

private:
        static unsigned int count;
        unsigned int id;

        Node *previous;
        Node *next;

        friend class boost::serialization::access;
    template<class Archive> void serialize(Archive & ar, const unsigned int version)
    {
                ar & BOOST_SERIALIZATION_NVP(id);

                ar & BOOST_SERIALIZATION_NVP(previous);
                ar & BOOST_SERIALIZATION_NVP(next);
    }
};

unsigned int Node::count = 0;

int _tmain(int argc, _TCHAR* argv[])
{
        Node *head = new Node();
        Node *node = new Node(head);
        node = new Node(node);
        node = new Node(node);

        // serialize
        {
                ofstream ofs("cyclic.xml");
                boost::archive::xml_oarchive oa(ofs);
                oa << BOOST_SERIALIZATION_NVP(head);
        }

        // deserialize
        Node *other_node = NULL;
        {
                ifstream ifs("cyclic.xml");
                boost::archive::xml_iarchive ia(ifs);
                ia >> BOOST_SERIALIZATION_NVP(other_node);
        }

        //quit
        return 0;
}