Re: [Boost-users] [serialization] 1.35 problem with explicitinstantiation

From: Robert Ramey (ramey_at_[hidden])
Date: 2008-04-12 21:44:23

I've updated the advice on using BOOST_CLASS_EXPORT.  The new
advice is described in the documentation in the trunk.  This will require 
moving some
macros between source modules (*.cpp and *.hpp  files).

In exchange, you'll get

a) a more carefully thought out way to handle exports.
b) the ability to include serialization code in DLLS with little or no 
suprises.
c) serialization code will be thread safe - without any locking required.

Robert Ramey

Dan Thill wrote:
> With 1.34, I was using the pattern described by Robert
> (http://lists.boost.org/boost-users/2006/01/16293.php) with
> non-intrusive serialization.  In short, the serialization functions
> are merely declared in the header files.  They are implemented in the
> .cpp file, and then explicitly instantiated for each archive type I'm
> using.
>
> However, with 1.35, this no longer works.  The export macros create an
> instance of the guid initializer as follows:
>
> export.hpp:150
>
> BOOST_PP_CAT(boost_serialization_guid_initializer_, __LINE__)
>
>
>
> However, this gives me redefinition errors in the following situaion:
>
> ClassA.h
> --------
> (line 1:) BOOST_CLASS_EXPORT(ClassA);
>
> ClassB.h
> --------
> (line 1: )BOOST_CLASS_EXPORT(ClassB);
>
>
>
> main.cpp
>
> #include <ClassA.h>
> #include <ClassB.h>
>
> (create an archive instance and attempt to serialize)
>
> -------------------------------
>
> As you can see, two objects, both named
> boost_serialization_guid_initializer_1,  will be created, and the
> compiler (MSVC80) will give me a redefinition error.
>
> I honestly have no idea what's going on.  This is so obvious, it has
> to mean that I'm organizing my code in some weird fashion.
>
> Thanks!
> Dan