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From: Felipe Magno de Almeida (felipe.m.almeida_at_[hidden])
Date: 2008-03-31 17:03:38

On Mon, Mar 31, 2008 at 6:35 PM, Robert Ramey <ramey_at_[hidden]> wrote:
> "Felipe Magno de Almeida" <felipe.m.almeida_at_[hidden]> wrote in message
> > On Mon, Mar 31, 2008 at 1:00 PM, Robert Ramey <ramey_at_[hidden]> wrote:


> >> I never considered the possibility that this would ever occur. I see
> >> no reason to ever do this and no reason why it should be difficult to
> >> avoid doing. I would say is a user error.
> >
> > What if someone wants to create serialization code for multiple
> > archives in different translation files? I know this is not *very*
> > compelling, but it is a honest use for multiple BOOST_CLASS_EXPORT.
> I would like to see BOOST_CLASS_EXPORT in the *.cpp file which
> contains the class definitions. There should only be one of those. Look
> at it this way - multiple definitions of the same function will give an
> error at link time - but here - link time is moved to runtime.

What if this happens:

-- src1.cpp

#include "type.hpp" // serialization type

#include <boost/archive/xml_iarchive.hpp>

BOOST_CLASS_EXPORT(type); // instantiates serialization for iarchive.hpp

-- src2.cpp

#include "type.hpp"

#include <boost/archive/xml_oarchive.hpp>

BOOST_CLASS_EXPORT(type); // instantiates serialization for oarchive.hpp

Why should this code be considered an error?
>  >>  I would like to trap it as such, but there is no way to distinguish it
>  >> from the
>  >>  legitimate case where the some type is exported from
>  >>  multiple DLLS.
>  >
>  > Changing std::multiset to std::set would be enough, wouldn't it?
>  Nope - that was exactly the problem.  If the same type is used
>  in different DLLS, then there will be multiple static objects created
>  each loaded/unloaded as the dlls themselves are loaded/unloaded.
But they will have different addresses won't they? The problem is with
the same instance
added twice to ktmap. Changing to std::set will allow the same type to
be added, but not the same
Also, I would like to suggest changing ktmap and tkmap to a more
descriptive name.
I know it is an implementation detail, but it is very easy to get confused when
debugging this.
>  Robert Ramey
Felipe Magno de Almeida

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