id,summary,reporter,owner,description,type,status,milestone,component,version,severity,resolution,keywords,cc
3977,Compile error on make_nvp with reference data member,kondo@…,Robert Ramey,"When I save the reference data member to the xml_archive by using make_nvp, the compile error occurs.

Attached file 'ref_direct.cpp' is an example program to reproduce problem.


{{{
#!cpp
    // Compile error!
    ar << boost::serialization::make_nvp(""ref_"", &p->ref_);
}}}

The error message is below.
{{{
error: invalid initialization of non-const reference of type ‘MyInt*&’ from a temporary of type ‘MyInt*'
}}}

We can avoid this error using additional variable or using static_cast.

{{{
#!cpp
    // OK
    MyInt* pRef = &p->ref_;
    ar << boost::serialization::make_nvp(""ref_"", pRef);
}}}

{{{
#!cpp
    // OK
    ar << boost::serialization::make_nvp(""ref_"", static_cast<const MyInt * const &>(&p->ref_));
}}}

But I think it's not elegant.

My idea is that introducing the new overload of make_nvp function template.

{{{
#!cpp
template<class T>
inline
#ifndef BOOST_NO_FUNCTION_TEMPLATE_ORDERING
const
#endif
nvp<const T> make_nvp(const char * name, const T & t){
    return nvp<const T>(name, t);
}
}}}

It resolves this problem.

Please check 'nvp_const_ref.patch' (attached file).

After apply the patch, I already did the regression test of serialization.
All test is passed.

My testing environments are 
g++ (Ubuntu 4.4.1-4ubuntu9) 4.4.1 and 
VC++ 9.0 on Windows7.
",Patches,closed,Boost 1.43.0,serialization,Boost 1.42.0,Problem,wontfix,,