David Abrahams wrote:
on Wed Nov 26 2008, Kenny Riddile <kfriddile-AT-yahoo.com> wrote:
#define BOOST_CLASS_EXPORT_GUID(T, K) \ namespace \ { \ ::boost::archive::detail::guid_initializer< T > const & \ BOOST_PP_CAT(boost_serialization_guid_initializer_, __LINE__) \ = ::boost::serialization::singleton< \ ::boost::archive::detail::guid_initializer< T > \ >::get_mutable_instance().export_guid(K); \ }
with:
#define BOOST_CLASS_EXPORT_GUID(T, K) \ namespace \ { \ ::boost::archive::detail::guid_initializer< T > const & \ BOOST_PP_CAT(boost_serialization_guid_initializer_, T) \
That will only work if T is a simple identifier or number. A name like std::pair<int,int> would fail.
I don't remember offhand whether class template specializations get exported by Boost.Serialization, but it seems to me that this doesn't need to be so hard in any case. You can probably make the namespace-scope variable a static member of a class template and use an explicit instantiation to generate it. If it works, there's no need for an unnamed namespace and no name clashes.
I tried this: template<class T> struct initialize_guid { static guid_initializer< T > const& guid; }; } // namespace detail } // namespace archive } // namespace boost #define BOOST_CLASS_EXPORT_GUID(T, K) \ template<> ::boost::archive::detail::guid_initializer< T > const& \ ::boost::archive::detail::initialize_guid<T>::guid = \ ::boost::serialization::singleton< \ ::boost::archive::detail::guid_initializer< T > \ >::get_mutable_instance().export_guid( K ); but, this only compiles when the macro is used from the global namespace. Otherwise VC++ gives an error similar to: error C2888: 'const boost::archive::detail::guid_initializer<T> &boost::archive::detail::initialize_guid<T>::guid' : symbol cannot be defined within namespace 'messenger' Changing the above code to: template<class T> struct initialize_guid { static guid_initializer< T > const& guid; }; template<class T> guid_initializer< T > const& initialize_guid< T >::guid = ::boost::serialization::singleton< ::boost::archive::detail::guid_initializer< T > >::get_mutable_instance().export_guid( BOOST_PP_STRINGIZE(T) ); } // namespace detail } // namespace archive } // namespace boost #define BOOST_CLASS_EXPORT_GUID(T, K) \ template struct ::boost::archive::detail::initialize_guid<T>; compiles, but breaks the existing public interface (K parameter is being ignored). Anyone have any suggestions?