[Boost-users] [serialization] Trouble serializing a bitfield

From: Ken Roser (boost_at_[hidden])
Date: 2006-11-22 16:17:13

Following is a very short program to test serialization along with the 
g++ output when compiling it.  My problem arises when I try to write a 
serialization function for a bitfield.  As the compiler output shows, 
the bitfield is the cause of this problem.

How should one serialize a bitfield?  Have I made some mistake in this 
code? 

I can get seriailziation to work if I instead use a save() and load() 
function that copies each bit to an int before archiving but I'm unsure 
if this is the best way.

#include <stdlib.h>
#include <string>
#include <iostream>
#include <sstream>

#include <boost/archive/archive_exception.hpp>
#include <boost/archive/binary_iarchive.hpp>
#include <boost/archive/binary_oarchive.hpp>
#include <boost/archive/text_iarchive.hpp>
#include <boost/archive/text_oarchive.hpp>
#include <boost/serialization/export.hpp>
#include <boost/serialization/serialization.hpp>
#include <boost/serialization/list.hpp>

class Event
{
    friend class boost::serialization::access;
    template<class Archive> void serialize(Archive &ar, const int version)
    {
        ar & bits;
        ar & field1;
    };
public:
    struct s
    {
        friend class boost::serialization::access;
        template<class Archive> void serialize(Archive &ar, const int 
version)
        {
            ar & spare1;
        };
        int    spare1 : 1;       
    } bits;
    int field1;
};

main(int argc, char **argv)
{
    Event *evt = new Event;
    evt->field1 = 0x1234;

    std::stringstream ofs;
    boost::archive::binary_oarchive oa(ofs);
    oa & *evt;        // serialize the event
}

serial2.cpp: In member function 'void Event::s::serialize(Archive&, int) 
[with Archive = boost::archive::binary_oarchive]':
boost/serialization/access.hpp:109:   instantiated from 'static void 
boost::serialization::access::serialize(Archive&, T&, unsigned int) 
[with Archive = boost::archive::binary_oarchive, T = Event::s]'
boost/serialization/serialization.hpp:81:   instantiated from 'void 
boost::serialization::serialize(Archive&, T&, unsigned int) [with 
Archive = boost::archive::binary_oarchive, T = Event::s]'
boost/serialization/serialization.hpp:140:   instantiated from 'void 
boost::serialization::serialize_adl(Archive&, T&, unsigned int) [with 
Archive = boost::archive::binary_oarchive, T = Event::s]'
boost/archive/detail/oserializer.hpp:147:   instantiated from 'void 
boost::archive::detail::oserializer<Archive, 
T>::save_object_data(boost::archive::detail::basic_oarchive&, const 
void*) const [with Archive = boost::archive::binary_oarchive, T = Event::s]'
serial2.cpp:43:   instantiated from here
serial2.cpp:29: error: cannot bind bitfield 
'((Event::s*)this)->Event::s::spare1' to 'int&'