Re: [boost] [serialization][1.36]ktmapcontainsextended_type_infowithm_key == 0

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
>  news:a2b17b60803311200v75904141rbe56c2713ef6fe7d_at_mail.gmail.com...
>
> > On Mon, Mar 31, 2008 at 1:00 PM, Robert Ramey <ramey_at_[hidden]> wrote:

[snip]

>  >>  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
instance.
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