[Boost-users] Re: Serialization, shared_ptr and namespaces

3 May 2005

      "Jan Eickmann" <je@framesys.de> wrote in message 
news:d58nee$rdh$1@sea.gmane.org...
...
Hello,
...
...
...
I'm trying to serialize a list of shared_ptr's to objects.
Here's a summary of the code I have:
namespace MyNamespace
{
class B
{
//implementation plus standard serialization function
};
class A
{
private:
    list< shared_ptr<B> > myBs;
public:
    template<class Archive>
    void serialize(Archive & ar, const unsigned int version)
    {
        ar & BOOST_SERIALIZATION_NVP(myBs);
    }
};
}
If I just try to serialize it, I get an unregistered_class exception. So 
I think I have to use BOOST_SHARED_POINTER_EXPORT(_GUID) to register the 
shared_ptr.
When I include this inside the namespace (please note that the error 
messages are from my real code, so they have slightly other names:
BOOST_SHARED_POINTER_EXPORT(B)
I get this:
 f:\xenocide\xenocide\src\common\simulation\simulation.h(108) : error 
C2059: syntax error : 'string'
f:\xenocide\xenocide\src\common\simulation\simulation.h(108) : error 
C2146: syntax error : missing ';' before identifier 
'BOOST_CLASS_EXPORT_GUID'
f:\xenocide\xenocide\src\common\simulation\simulation.h(108) : error 
C2059: syntax error : 'string'
f:\xenocide\xenocide\src\common\simulation\simulation.h(109) : error 
C2143: syntax error : missing ';' before '}'
When I put it outside the namespace I have to use a fully qualified name 
including the namespace for class B, so it becomes
BOOST_SHARED_POINTER_EXPORT(MyNamespace::B)
Then I get (not Xenocide is here what MyNamespace is in my example):
f:\xenocide\xenocide\src\common\simulation\simulation.h(115) : error 
C2653: '__shared_ptr_Xenocide' : is not a class or namespace name
f:\xenocide\xenocide\src\common\simulation\simulation.h(115) : error 
C2653: '__shared_ptr_Xenocide' : is not a class or namespace name
I also tried various combinations with BOOST_SHARED_POINTER_EXPORT_GUID 
but it didn't help.
Can someone explain to me how I have to declare shared_ptr's in order for 
them to work with boost::serialization? I was unable to find some more 
indepth documentation.
I've modified shared_ptr.hpp as follows:

// This macro is used to export GUIDS for shared pointers to allow
// the serialization system to export them properly. David Tonge
//#define BOOST_SHARED_POINTER_EXPORT_GUID(T, K)    \
//    typedef boost::detail::sp_counted_base_impl<  \
//        T *,                                      \
//        boost::checked_deleter< T >               \
//    > __shared_ptr_ ## T;                         \
//    BOOST_CLASS_EXPORT_GUID(__shared_ptr_ ## T, "__shared_ptr_" K)\
//    BOOST_CLASS_EXPORT_GUID(T, K)                 \
//    /**/
/**/
#define BOOST_SHARED_POINTER_EXPORT_GUID(T,N)     \
    typedef boost::detail::sp_counted_base_impl<  \
        T *,                                      \
        boost::checked_deleter< T >               \
    > __shared_ptr_ ## N;                         \
    BOOST_CLASS_EXPORT(__shared_ptr_ ## N)        \
    BOOST_CLASS_EXPORT(T)                         \
/**/

#define BOOST_SHARED_POINTER_EXPORT(T)            \
    BOOST_SHARED_POINTER_EXPORT_GUID(             \
        T,                                        \
        BOOST_PP_STRINGIZE(T)                     \
    )                                             \
    /**/

#endif // BOOST_SERIALIZATION_SHARED_PTR_HPP

Then I've got a separate .cpp file and use like so:

#define BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP

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

#include <boost/serialization/export.hpp>

...

BOOST_SHARED_POINTER_EXPORT_GUID( Adv::CAssembly, AdvCAssembly );

This allows me to serialize shared_ptr<Adv::CAssembly>'s properly. The 
BOOST_NO_ARGUMENT_DEPENDENT_LOOKUP is necessary to avoid MSVC7.1 compiler 
crashes with boost 1.32.

I mentioned this to Robert Ramey some time back. I'm not sure if these 
changes were made to the CVS.

Jeff Flinn