Re: [Boost-users] Serialization recursive include problem

30 Sep 2007

      Honestly I have been looking for a solution for hours before I made this
post. I am not so familiar with boost, the only module I use is
serialization so maybe my error is obvious but I went through all the doc on
boost.org without luck.

I should have been more descriptive I my first post. I does not work because
I get unresolved externals on the base class save / load functions when I
implement the derived class save/load functions. I am using the intrusive
version of serialization so their should be no particular namespace
requirement. Here is a simplified example of my problem:

///////////////////////////////////// A.h
Class A:
{
    friend class boost::serialization::access;
    template<class Archive>
    void save(Archive & ar, const unsigned int version) const;
    template<class Archive>
    void load(Archive & ar, const unsigned int version);

    BOOST_SERIALIZATION_SPLIT_MEMBER()

};
/////////////////////////////////////

///////////////////////////////////// B.h
class B: public A
{
    friend class boost::serialization::access;
    template<class Archive>
    void save(Archive & ar, const unsigned int version) const;

    template<class Archive>
    void load(Archive & ar, const unsigned int  file_version );

    BOOST_SERIALIZATION_SPLIT_MEMBER()
}
BOOST_CLASS_EXPORT_GUID(B, "B")
/////////////////////////////////////

///////////////////////////////////// A.cpp
template<class Archive>
void A::save(Archive & ar, const unsigned int version) const
{
    ar & var1;
}

template<class Archive>
void A::load(Archive & ar, const unsigned int  file_version )
{
    ar & var;
    somestuff();
}
/////////////////////////////////////

///////////////////////////////////// B.cpp
template<class Archive>
void B::save(Archive & ar, const unsigned int version) const
{
    ar & boost::serialization::base_object<A>(*this);
    ar & var2;
}

template<class Archive>
void B::load(Archive & ar, const unsigned int  file_version )
{
    ar & boost::serialization::base_object<A>(*this);
    ar & var2;
    morestuff();
}
 /////////////////////////////////////

If I don't put the two implementation of serialization of A and B in the
same file I get this error:

error LNK2019: unresolved external symbol "public: void __thiscall
A::save<class boost::archive::text_oarchive> ...
error LNK2019: unresolved external symbol "public: void __thiscall
A::load<class boost::archive::text_iarchive> ...

Feel free to redirect me to some more documentation, I read most of
boost.org serialization section but maybe their are other places to look at.

I am also having problem figuring out the when to use BOOST_CLASS_EXPORT vs
BOOST_CLASS_EXPORT_GUID vs ar.register_types.

Thank you for your help.

On 9/30/07, Robert Ramey  wrote:
...
A easy way to fix this would be to put the serialization code in the
source file instead of the header file but I can't get this to work...
There is no reason why this shouldn't work.  Invest some effort figuring
out why it won't link.  Check namespaces.
Robert Ramey
"Fred Lupien"  wrote in message
news:32e6d6bf0709300738u77850377t2bf40ec5501b882f@mail.gmail.com...
Hi,
I am using the boost serialization library in a personal project and
ran into a recursive include problem. Class A serialize an object of class B
and class B also serialize an object of class A. So class A must be a
complete type in class B and class B must be a complete type in class A,
hence the recursive include problem. I always end up with unresolved
externals if the body of my serialization functions are not within the
header file. Any way around this beside switching to non-intrusive
serialization?
thanx!
--
Frédérick Martel-Lupien
Étudiant en Génie Informatique
Université de Sherbrooke
fred.lupien@gmail.com
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-- 
Frédérick Martel-Lupien
Étudiant en Génie Informatique
Université de Sherbrooke
fred.lupien@gmail.com