Re: [Boost-users] [Serialization] Multiple BOOST_CLASS_EXPORT

From: Sohail Somani (s.somani_at_[hidden])
Date: 2007-04-28 17:03:27

> -----Original Message-----
> From: boost-users-bounces_at_[hidden] 
> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Robert Ramey
> Sent: Friday, April 27, 2007 9:47 PM
> To: boost-users_at_[hidden]
> Subject: Re: [Boost-users] [Serialization] Multiple BOOST_CLASS_EXPORT
> 
> Sohail Somani wrote:
> >> -----Original Message-----
> >> From: boost-users-bounces_at_[hidden]
> >> [mailto:boost-users-bounces_at_[hidden]] On Behalf Of Robert

> > If you have BOOST_CLASS_EXPORT in a header file, doesn't that cause
> > the same problems? If this is what your checkins would fix, then
> > that's understandable.
> 
> No - code is only instatiated for archives actually used.  So 
> if the usage
> of an archive is confined to ONE module there are no problems.  But
> this requires instatiating the serialization functions not in 
> the header - 
> that
> is in "out of line" code.  Its quite doable but somewhat 
> annoying.  This
> is a result of the C++ instantiation model.  Note that 
> different compilers
> and linkers do things differently, but I believe that this 
> method works
> on all of them.
> 
> Downside you have to explictly instantiate combination of type/archive
> you might export.  So I recommend putting them in a library and
> linking against that so you don't suffer from code bloat.

Well the way I work is I define the class in the hpp file with
template<typename Archive> void serialize(...);

Then in the cpp file I do (something like):

#include "myclass.hpp"
#include "all_my_archives.hpp"
#include "export.hpp"

template<typename Archive>
void MyClass::serialize(...){...}

BOOST_CLASS_EXPORT(MyClass);

So I think I'm already doing what you suggest as all my classes get
compiled once into a single library.

> Finally, you can also use the polymorphic version of the archive.
> This permits you to compile only one instantiation for all 
> archive types. 
> Linking
> is accomplished at runtime via a virtual function interface.

In time, I think I will do that. Had some issues when I tried to do it
earlier but didn't bother to figure them out as I only need a single
archive type.

Thanks,

Sohail