RE: [Boost-users] Re: Re: Serialization when using virtual inheritance

From: Eric (eric-public_at_[hidden])
Date: 2005-05-30 13:33:21

Hi Robert (and Jeff):

> Actually, the export.hpp has to come after any *archive.hpp 
> due to the "trick" used to instantiate the appropriate code.

That was the problem!  I only used the xml_oarchive object in the main()
function, so I only included the respective headers in the main.  The rest
of the code included the export.hpp header.  So, I changed my common include
file to also include the *archive.hpp headers and everything is working
well.

The only thing that I've noticed is that sometimes the objects won't be
found when I have 2 or more abstract classes between the base and the final
concrete object.  The concrete object is registered, but it looks like the
(Derived,Base) pair isn't being found.  Any advice on where I went wrong on
that is appreciated.  In the meantime, I'm using void_cast_register<>(...)
to register the base class and the top derived class and everything works
great so far :)

-Eric

> 
> On some compilers, one can get multiple symbol errors.  I
> think the only way to handle this is to be sure its
> included at most once or tweak the linker switches to 
> override the error.

> Robert Ramey

>> "Eric" <eric-public_at_[hidden]> wrote in
>> message news:001601c564d9$35709a60$0a00a8c0_at_FASTBRICK...
>> Thanks Robert.  This partially worked...  Your 
>> comment about putting the BOOST_CLASS_EXPORT 
>> macro into the header keyed me into something.

>> I am using the BOOST_CLASS_EXPORT(derived) macro, but
>> I've been placing them into the source (cpp) file instead
>> of the header (h) file.  With my system, when I put 
>> BOOST_CLASS_EXPORT(derived) into the header file, I 
>> get a multiply-defined error at link time (the offending 
>> code is boost::archive::detail::guid_initializer<class,...> 
>> since the header is included multiple times when I use the 
>> class.
>> 
>> As a test, I setup a sandbox with a stripped down system
>>  and was able to get it to work when I put the 
>> BOOST_CLASS_EXPORT in the header, but not when it is
>> in the cpp file.
>> 
>> Q:  Why does the location of the BOOST_CLASS_EXPORT
>> matter?  Is it doing order-depended initialization
>> upon bringing up the system?
>> 
>> 
>> Q:  How do I avoid the mutiple defined error in
>> the linker?
>> 
>> 
>> Thanks again for your help and the library :)
>> 
>> -Eric