Re: [Boost-users] Serialization with polymorphic_*_archiveandBOOST_CLASS_EXPORT

7 Nov 2006

      Thanks for your swift reply!

In my example with the non-templated serialize with polymorphic_iarchive
the statement BOOST_CLASS_EXPORT(B) fails to compile. It compiles
fine without that statement, but fails to serialize with asserion:
Assertion failed: NULL != bpos_ptr, file
include\boost\archive\detail\oserializer.hpp, line 418
If I manully register B with register_type it works.

I'm using VC8 and boost 1.33.1 and I've attached the error message from
compiling.

-- Anders

1>Compiling...
1>_main.cpp
1>include\boost\serialization\access.hpp(109) : error C2664: 'void
B::serialize(boost::archive::polymorphic_iarchive &,const unsigned int)' :
cannot convert parameter 1 from 'boost::archive::text_oarchive' to
'boost::archive::polymorphic_iarchive &'
1>        include\boost\serialization\serialization.hpp(81) : see reference
to function template instantiation 'void
boost::serialization::access::serialize(Archive &,T &,const
unsigned int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\serialization.hpp(140) : see reference
to function template instantiation 'void
boost::serialization::serialize(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(152) : see reference
to function template instantiation 'void
boost::serialization::serialize_adl(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(145) : while
compiling class template member function 'void
boost::archive::detail::oserializer::save_object_data(boost::archive::detail::basic_oarchive

&,const void *) const'
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(163) : see reference
to class template instantiation
'boost::archive::detail::oserializer' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(162) : while
compiling class template member function 'const
boost::archive::detail::basic_oserializer
&boost::archive::detail::pointer_oserializer::get_basic_serializer(void)
const'
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::text_oarchive
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(515) : see reference
to class template instantiation
'boost::archive::detail::pointer_oserializer' being compiled
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::text_oarchive
1>        ]
1>        include\boost\serialization\export.hpp(86) : see reference to
function template instantiation 'const
boost::archive::detail::basic_pointer_oserializer
&boost::archive::detail::instantiate_pointer_oserializer(Archive
*,T *)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(82) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::o::invoke(void)'
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(105) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive::o' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(89) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::instantiate(void)'
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(116) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(115) : while compiling
class template member function 'void
boost::archive::detail::export_impl::for_each_archive::instantiate(void)'
1>        with
1>        [
1>            ASeq=boost::archive::detail::known_archive_types::type,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(132) : see reference to
class template instantiation
'boost::archive::detail::export_impl::for_each_archive' being
compiled
1>        with
1>        [
1>            ASeq=boost::archive::detail::known_archive_types::type,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(131) : while compiling
class template member function
'boost::archive::detail::export_generator::export_generator(void)'
1>        with
1>        [
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>        include\boost\serialization\export.hpp(177) : see reference to
class template instantiation
'boost::archive::detail::export_generator' being compiled
1>        with
1>        [
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>        include\boost\serialization\export.hpp(176) : while compiling
class template member function 'const
boost::archive::detail::export_generator
*boost::archive::detail::export_instance::not_abstract::invoke(void)'
1>        with
1>        [
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>        include\boost\serialization\export.hpp(192) : see reference to
class template instantiation
'boost::archive::detail::export_instance::not_abstract' being
compiled
1>        with
1>        [
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>        include\boost\serialization\export.hpp(211) : see reference to
function template instantiation 'std::pair<_Ty1,_Ty2>
boost::archive::detail::export_instance_invoke(void)' being compiled
1>        with
1>        [
1>            _Ty1=const
boost::archive::detail::export_generator

*,
1>            _Ty2=const boost::archive::detail::guid_initializer<B> *,
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>        include\boost\serialization\export.hpp(210) : while compiling
class template member function 'std::pair<_Ty1,_Ty2>
boost::archive::detail::export_archives::non_empty_archive_list::invoke(void)'
1>        with
1>        [
1>            _Ty1=const
boost::archive::detail::export_generator

*,
1>            _Ty2=const boost::archive::detail::guid_initializer<B> *,
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>        include\boost\serialization\export.hpp(225) : see reference to
class template instantiation
'boost::archive::detail::export_archives::non_empty_archive_list'
being compiled
1>        with
1>        [
1>            T=B,
1>            ASeq=boost::archive::detail::known_archive_types::type
1>        ]
1>
c:\users\awk\desktop\work\code\src\tests\scenegraph_regression\_main.cpp(129)
: see reference to function template instantiation 'std::pair<_Ty1,_Ty2>
boost::archive::detail::export_archives_invoke(B

&,boost::archive::detail::known_archive_types::type &)' being compiled
1>        with
1>        [
1>            _Ty1=const
boost::archive::detail::export_generator

*,
1>            _Ty2=const boost::archive::detail::guid_initializer<B> *
1>        ]
1>include\boost\serialization\access.hpp(109) : error C2664: 'void
B::serialize(boost::archive::polymorphic_iarchive &,const unsigned int)' :
cannot convert parameter 1 from 'boost::archive::text_iarchive' to
'boost::archive::polymorphic_iarchive &'
1>        include\boost\serialization\serialization.hpp(81) : see reference
to function template instantiation 'void
boost::serialization::access::serialize(Archive &,T &,const
unsigned int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\serialization.hpp(140) : see reference
to function template instantiation 'void
boost::serialization::serialize(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(164) : see reference
to function template instantiation 'void
boost::serialization::serialize_adl(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(157) : while
compiling class template member function 'void
boost::archive::detail::iserializer::load_object_data(boost::archive::detail::basic_iarchive

&,void *,const unsigned int) const'
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(175) : see reference
to class template instantiation
'boost::archive::detail::iserializer' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(174) : while
compiling class template member function 'const
boost::archive::detail::basic_iserializer
&boost::archive::detail::pointer_iserializer::get_basic_serializer(void)
const'
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::text_iarchive
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(546) : see reference
to class template instantiation
'boost::archive::detail::pointer_iserializer' being compiled
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::text_iarchive
1>        ]
1>        include\boost\serialization\export.hpp(78) : see reference to
function template instantiation 'const
boost::archive::detail::basic_pointer_iserializer
&boost::archive::detail::instantiate_pointer_iserializer(Archive
*,T *)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(74) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::i::invoke(void)'
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(105) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive::i' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(89) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::instantiate(void)'
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(116) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive' being compiled
1>        with
1>        [
1>            Archive=boost::archive::text_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(115) : while compiling
class template member function 'void
boost::archive::detail::export_impl::for_each_archive::instantiate(void)'
1>        with
1>        [
1>
ASeq=boost::mpl::list5boost::archive::text_iarchive,boost::archive::xml_oarchive,boost::archive::x...,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(122) : see reference to
class template instantiation
'boost::archive::detail::export_impl::for_each_archive' being
compiled
1>        with
1>        [
1>
ASeq=boost::mpl::list5boost::archive::text_iarchive,boost::archive::xml_oarchive,boost::archive::x...,
1>            T=B
1>        ]
1>include\boost\serialization\access.hpp(109) : error C2664: 'void
B::serialize(boost::archive::polymorphic_iarchive &,const unsigned int)' :
cannot convert parameter 1 from 'boost::archive::xml_oarchive' to
'boost::archive::polymorphic_iarchive &'
1>        include\boost\serialization\serialization.hpp(81) : see reference
to function template instantiation 'void
boost::serialization::access::serialize(Archive &,T &,const
unsigned int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\serialization.hpp(140) : see reference
to function template instantiation 'void
boost::serialization::serialize(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(152) : see reference
to function template instantiation 'void
boost::serialization::serialize_adl(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(145) : while
compiling class template member function 'void
boost::archive::detail::oserializer::save_object_data(boost::archive::detail::basic_oarchive

&,const void *) const'
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(163) : see reference
to class template instantiation
'boost::archive::detail::oserializer' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(162) : while
compiling class template member function 'const
boost::archive::detail::basic_oserializer
&boost::archive::detail::pointer_oserializer::get_basic_serializer(void)
const'
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::xml_oarchive
1>        ]
1>        include\boost\archive\detail\oserializer.hpp(515) : see reference
to class template instantiation
'boost::archive::detail::pointer_oserializer' being compiled
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::xml_oarchive
1>        ]
1>        include\boost\serialization\export.hpp(86) : see reference to
function template instantiation 'const
boost::archive::detail::basic_pointer_oserializer
&boost::archive::detail::instantiate_pointer_oserializer(Archive
*,T *)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(82) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::o::invoke(void)'
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(105) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive::o' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(89) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::instantiate(void)'
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(116) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_oarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(115) : while compiling
class template member function 'void
boost::archive::detail::export_impl::for_each_archive::instantiate(void)'
1>        with
1>        [
1>
ASeq=boost::mpl::list4boost::archive::xml_oarchive,boost::archive::xml_iarchive,boost::archive::po...,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(122) : see reference to
class template instantiation
'boost::archive::detail::export_impl::for_each_archive' being
compiled
1>        with
1>        [
1>
ASeq=boost::mpl::list4boost::archive::xml_oarchive,boost::archive::xml_iarchive,boost::archive::po...,
1>            T=B
1>        ]
1>include\boost\serialization\access.hpp(109) : error C2664: 'void
B::serialize(boost::archive::polymorphic_iarchive &,const unsigned int)' :
cannot convert parameter 1 from 'boost::archive::xml_iarchive' to
'boost::archive::polymorphic_iarchive &'
1>        include\boost\serialization\serialization.hpp(81) : see reference
to function template instantiation 'void
boost::serialization::access::serialize(Archive &,T &,const
unsigned int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\serialization.hpp(140) : see reference
to function template instantiation 'void
boost::serialization::serialize(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(164) : see reference
to function template instantiation 'void
boost::serialization::serialize_adl(Archive &,T &,const unsigned
int)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(157) : while
compiling class template member function 'void
boost::archive::detail::iserializer::load_object_data(boost::archive::detail::basic_iarchive

&,void *,const unsigned int) const'
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(175) : see reference
to class template instantiation
'boost::archive::detail::iserializer' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(174) : while
compiling class template member function 'const
boost::archive::detail::basic_iserializer
&boost::archive::detail::pointer_iserializer::get_basic_serializer(void)
const'
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::xml_iarchive
1>        ]
1>        include\boost\archive\detail\iserializer.hpp(546) : see reference
to class template instantiation
'boost::archive::detail::pointer_iserializer' being compiled
1>        with
1>        [
1>            T=B,
1>            Archive=boost::archive::xml_iarchive
1>        ]
1>        include\boost\serialization\export.hpp(78) : see reference to
function template instantiation 'const
boost::archive::detail::basic_pointer_iserializer
&boost::archive::detail::instantiate_pointer_iserializer(Archive
*,T *)' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(74) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::i::invoke(void)'
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(105) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive::i' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(89) : while compiling class
template member function 'void
boost::archive::detail::export_impl::archive::instantiate(void)'
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(116) : see reference to
class template instantiation
'boost::archive::detail::export_impl::archive' being compiled
1>        with
1>        [
1>            Archive=boost::archive::xml_iarchive,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(115) : while compiling
class template member function 'void
boost::archive::detail::export_impl::for_each_archive::instantiate(void)'
1>        with
1>        [
1>
ASeq=boost::mpl::list3boost::archive::xml_iarchive,boost::archive::polymorphic_oarchive,boost::arc...,
1>            T=B
1>        ]
1>        include\boost\serialization\export.hpp(122) : see reference to
class template instantiation
'boost::archive::detail::export_impl::for_each_archive' being
compiled
1>        with
1>        [
1>
ASeq=boost::mpl::list3boost::archive::xml_iarchive,boost::archive::polymorphic_oarchive,boost::arc...,
1>            T=B
1>        ]

----- Original Message ----- 
From: "Robert Ramey" 
Newsgroups: gmane.comp.lib.boost.user
Sent: Tuesday, November 07, 2006 2:42 AM
Subject: Re: Serialization with polymorphic_*_archiveandBOOST_CLASS_EXPORT
...
Anders Wang Kristensen wrote:
...
Hi,
I'm having trouble serializing through the a pointer to the base as
shown below.
If I manually register class B with template register_type<B>() it
works, but I
would rather use the BOOST_CLASS_EXPORT macros since that is more
convenient.
Unfortunately BOOST_CLASS_EXPORT  assumes you are using the templated
version of serialize, and not polymorphic_iarchive/oarchive, that I'm
using.
I don't think that's true. Maybe you mean it assums you are using
member serialize functions - but that won't be true either.
Basically I think your example should function.  Where does it fail?
Does it throw and exception? where? does the assert fail?, etc.,etc.
Also what compiler, os, version of boost etc.?
Though its beside the point, I would also make your example more portable 
wit the fillowing
changes:
...
struct A {
   template<class Archive>
   void serialize(Archive & ar, const unsigned int file_version);
   ...
};
template<class Archive>
void A::serialize(Archive & ar, const unsigned int file_version){
   ar & BOOST_SERIALIZATION_NVP(data);
}
struct B : public A {
   template<class Archive>
   void serialize(Archive & ar, const unsigned int file_version);
   ...
};
template<class Archive>
void B::serialize(Archive & ar, const unsigned int file_version){
   ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(A);
   ar & BOOST_SERIALIZATION_NVP(foo);
}
BOOST_CLASS_EXPORT(B)
int main(int argc, const char* argv[]){
   boost::shared_ptr<A> a(new B);
   boost::shared_ptr<A> a1;
   std::stringstream ss;
  {
       boost::archive::polymorphic_text_oarchive oa(ss);
       //oa.template register_type<B>();
      oa << BOOST_SERIALIZATION_NVP(a);
   }
   try{
       boost::archive::polymorphic_text_iarchive ia(ss);
       //ia.template register_type<B>();
       ia >> BOOST_SERIALIZATION_NVP(a1);
   }
   catch(...){
       ...
   }
   B* x = dynamic_cast(a.get());
   B* y = dynamic_cast(b.get());
assert(*x == *y);
   return 0;
}
----- Original Message ----- 
From: "Robert Ramey" 
Newsgroups: gmane.comp.lib.boost.user
Sent: Tuesday, November 07, 2006 2:42 AM
Subject: Re: Serialization with polymorphic_*_archiveandBOOST_CLASS_EXPORT
...
Anders Wang Kristensen wrote:
...
Hi,
I'm having trouble serializing through the a pointer to the base as
shown below.
If I manually register class B with template register_type<B>() it
works, but I
would rather use the BOOST_CLASS_EXPORT macros since that is more
convenient.
Unfortunately BOOST_CLASS_EXPORT  assumes you are using the templated
version of serialize, and not polymorphic_iarchive/oarchive, that I'm
using.
I don't think that's true. Maybe you mean it assums you are using
member serialize functions - but that won't be true either.
Basically I think your example should function.  Where does it fail?
Does it throw and exception? where? does the assert fail?, etc.,etc.
Also what compiler, os, version of boost etc.?
Though its beside the point, I would also make your example more portable 
wit the fillowing
changes:
...
struct A {
   template<class Archive>
   void serialize(Archive & ar, const unsigned int file_version);
   ...
};
template<class Archive>
void A::serialize(Archive & ar, const unsigned int file_version){
   ar & BOOST_SERIALIZATION_NVP(data);
}
struct B : public A {
   template<class Archive>
   void serialize(Archive & ar, const unsigned int file_version);
   ...
};
template<class Archive>
void B::serialize(Archive & ar, const unsigned int file_version){
   ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(A);
   ar & BOOST_SERIALIZATION_NVP(foo);
}
BOOST_CLASS_EXPORT(B)
int main(int argc, const char* argv[]){
   boost::shared_ptr<A> a(new B);
   boost::shared_ptr<A> a1;
   std::stringstream ss;
  {
       boost::archive::polymorphic_text_oarchive oa(ss);
       //oa.template register_type<B>();
      oa << BOOST_SERIALIZATION_NVP(a);
   }
   try{
       boost::archive::polymorphic_text_iarchive ia(ss);
       //ia.template register_type<B>();
       ia >> BOOST_SERIALIZATION_NVP(a1);
   }
   catch(...){
       ...
   }
   B* x = dynamic_cast(a.get());
   B* y = dynamic_cast(b.get());
assert(*x == *y);
   return 0;
}