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

From: Robert Ramey (ramey_at_[hidden])
Date: 2007-10-11 11:57:05

This is my concern as well.

I am interested in addressing this in a definitive way.  But its not trivial
to do a good job which can be proven to work while at the same time
not adding a performance hit to every user of the package.

Robert Ramey

Sergey Skorniakov wrote:
>> 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< i mplemented 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<.