boost serialization problem with reference members

From:
"Abhishek Padmanabh" <abhishek.padmanabh@gmail.com>
Newsgroups:
comp.lang.c++
Date:
21 Feb 2007 08:55:34 -0800
Message-ID:
<1172076928.967834.21280@p10g2000cwp.googlegroups.com>
I have been trying out boost's serialization library for the past few
days. And I have come across a problem serializing a class that has a
reference member. The code is posted as below:

[CODE]
#include <iostream>
#include <fstream>
#include <string>

#include <boost/archive/xml_iarchive.hpp>
#include <boost/archive/xml_oarchive.hpp>

//for name value pairs when doing XML archiving
#include <boost/serialization/nvp.hpp>

class MyClassWithNoDefaultConstructor;
std::ostream& operator<<(std::ostream& os, const
MyClassWithNoDefaultConstructor& object);

//global integer variable... whose reference will be a member of
MyClassWithNoDefaultConstructor
int global_int = 10;

class MyClassWithNoDefaultConstructor
{
    public:
        MyClassWithNoDefaultConstructor(int i, int& ref_)
            : intMember(i), ref(ref_)
        {}
    private:
        int intMember;
        int& ref;
        template<class Archive>
        void serialize(Archive& ar, const unsigned int version)
        {
            ar & BOOST_SERIALIZATION_NVP(intMember);
            ar & BOOST_SERIALIZATION_NVP(ref);
        }
    friend class boost::serialization::access;
    friend std::ostream& operator<<(std::ostream& os, const
MyClassWithNoDefaultConstructor& object);
};

std::ostream& operator<<(std::ostream& os, const
MyClassWithNoDefaultConstructor& object)
{
    os << "\nMyClassWithNoDefaultConstructor contents:\n";
    os << "intMember - " << object.intMember << "\n";
    os << "ref - " << object.ref << "\n";
    return os;
}

namespace boost
{
    namespace serialization
    {
        template<class Archive>
        inline void save_construct_data(Archive & ar, const
MyClassWithNoDefaultConstructor* t, const unsigned int file_version)
        {
            // save data required to construct instance
            ar << t->intMember;
            ar << &(t->ref);
        }

        template<class Archive>
        inline void load_construct_data(Archive & ar,
MyClassWithNoDefaultConstructor* t, const unsigned int file_version)
        {
            // retrieve data from archive required to construct new instance
            int m;
            //int * ptr;
            int * ptr = new int();
            ar >> m;
            ar >> ptr;
            ::new(t)MyClassWithNoDefaultConstructor(m, *ptr);
        }
    }
}

void SerializeMyClassWithNoDefaultConstructor(const std::string&
filename)
{
    MyClassWithNoDefaultConstructor object(111, global_int);
    std::ofstream ofs(filename.c_str());
    assert(ofs.good());
    boost::archive::xml_oarchive xml_oa(ofs);
    xml_oa << BOOST_SERIALIZATION_NVP(object);
}

void DeserializeMyClassWithNoDefaultConstructor(const std::string&
filename)
{
    char * buffer = new char[sizeof(MyClassWithNoDefaultConstructor)];
    MyClassWithNoDefaultConstructor* ptr =
reinterpret_cast<MyClassWithNoDefaultConstructor*>(buffer);
    std::ifstream ifs(filename.c_str());
    assert(ifs.good());
    std::cout << "inside deserialize()" << std::endl;
    boost::archive::xml_iarchive xml_ia(ifs);
    std::cout << "xml_iarchive constructed" << std::endl;
    xml_ia >> BOOST_SERIALIZATION_NVP(*ptr);
    std::cout << "deserialized" << std::endl;
    std::cout << *ptr;
    ptr->~MyClassWithNoDefaultConstructor();
    delete[] buffer;
    buffer=NULL; ptr=NULL;
}

int main()
{
    const std::string filenameMyClassWithNoDefaultConstructor="/tmp/
testfileMyClassWithNoDefaultConstructor.xml";
    try
    {

SerializeMyClassWithNoDefaultConstructor(filenameMyClassWithNoDefaultConstructor);

DeserializeMyClassWithNoDefaultConstructor(filenameMyClassWithNoDefaultConstructor);
    }
    catch(const boost::archive::archive_exception& ex)
    {
        std::cout << ex.what() << "\n";
    }
    catch(const std::exception& ex)
    {
        std::cout << ex.what() << "\n";
    }
    return 0;
}

It compiles fine with g++ 3.4.6. But fails with a segmentation fault.
I tried fiddling around with it but the best I can do is cause it to
fail with a bus error or a stream error. Here is the documentation
that I am referring to - http://www.boost.org/libs/serialization/doc/index.html.
For reference members, the specific documentation page is -
http://www.boost.org/libs/serializa...html#references

The code works (or atleast it seems to) if you remove the reference
member. That is, I have it working for classes that don't have a
default constructor but what if there are constant or reference
members? The documentation seems to suggest it is possible to handle
them as are non-default constructor classes are, but I am not able to
get it to work.

Am I doing something silly there? Or is there a major gap between my
understanding and what the documentation says? I am using boost 1.32 -
can that be a reason? Can anyone help with the problem?

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