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

From: Jeff Flinn (TriumphSprint2000_at_[hidden])
Date: 2005-05-03 16:06:44

"Jan Eickmann" <je_at_[hidden]> wrote in message 
news:d58nee$rdh$1_at_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