Re: [Boost-users] [serialization] shared libraries & extended_type_info registration

From: Sergey Skorniakov (s.skorniakov_at_[hidden])
Date: 2007-10-11 06:06:23

> Thank you for your answer. My application is mono thread and duplicated 
> code for seralization is granted to be the same. Our code actually 
> forbide this design. What about replacing line 74&75 of
> 
> extended_type_info.cpp :
> 74        assert(lookup(eti) == m_self->m_map.end());
> 75         m_self->m_map.insert(eti);
> 
> by
> 
> if ( lookup(eti) == m_self->m_map.end() )
> {
>    m_self->m_map.insert(eti);
> }
> 
> ? With this new behavior the same type_info can be registred several time.
> 
> 
> With this modification my design work fine. I can send you a sample of 
> code if you want to investigate the problem
> 

This modification will just leads to hard-to-find bugs. Take a look how this information is used in the library - for example, void_caster_compare uses extended_type_info::operator< and it will works wrong (results will be similar as derived class is not registered), because same type infos will be treated as different. Comparison of extended_type_info are also used in basic_archive_impl::helper_compare, in basic_serializer::operator< and may be in some other places. Thus, to support multiple registration, you should provide such extended_type_info::operator< implementation that duplicated type infos from different libs will be equivalent. I had just added double-linked list of extended_type_info to extended_type_info and adds duplicated type infos to the tail of this list. For operator< implemented as comparison of lists heads (first registered type info).
Also, modification of basic_serializer::operator< required because it compares addresses of type infos instead of using extended_type_info::operator<.