Re: [boost] [serialization] problem withboost/serialization/is_abstract.hpp

From: Aleksey Gurtovoy (agurtovoy_at_[hidden])
Date: 2004-11-04 13:58:14

Joaquín Mª López Muñoz writes:
> In MSVC 6.0, the following snippet fails:
>
> #include <boost/archive/text_iarchive.hpp>
> #include <boost/tuple/tuple.hpp>

A straightforward

#include <boost/type_traits/is_abstract.hpp>

would do as well.

>
> int main()
> {
>   return 0;
> }
>
> complaining about is_abstract being already defined. The problem
> lies in the following lines inside boost/serialization/is_abstract.hpp:
>
> #ifndef BOOST_TT_IS_ABSTRACT_CLASS_HPP
> #if    defined(__GNUC__) && (34 <= _GNUC__ * 10 + __GNU_MINOR)  \
>     || defined(__MSVC_VER) && (1310 <= __MSVC_VER)              \
>     || defined(__EDG_VERSION__)                                 \
>     /**/
>     #include <boost/type_traits/is_abstract.hpp>
> #else

First of all, the whole thing is a huge hack and can cause an ODR
violation on 1-2-3. We should really fix type_traits to fall back to
something like the code below, but that is definitely out for the
release.

Having said that, the #else branch is simply missing this:

#   define BOOST_TT_IS_ABSTRACT_CLASS_HPP

> // default to false if not supported
>     namespace boost {
>     template<class T>
>     struct is_abstract {
>         typedef mpl::bool_<false> type;
>         BOOST_STATIC_CONSTANT(bool, value = is_abstract::type::value);
>     };
>     } // namespace boost
> #endif
> #endif // BOOST_TT_IS_ABSTRACT_CLASS_HPP
>
> The code is *incorrectly* using __MSVC_VER where it should use
> _MSVC_VER (just one leading underscore). Thus boost::is_abstract is
> defined twice, as boost/type_traits.hpp is implicitly included by
> boost/tupe/tuple.hpp

It's getting defined twice because of the missing define above, not
because of the misspelling, but the latter would be good to fix, too.

> If nobody complains, I can fix this and commit it to the release and
> main branch.

Please! Together with the #define, if you can.

> What worries me, though, is that the code above seems flawed to me
> (apart from the minor typo). What happens if the compiler is not one of
> those taken care of explicitly in boost/serialization/is_abstract.hpp?
> Could anyone please test the first snippet in some compiler other than
> MSVC, ICC for Windows, GCC or an EDG-based compiler? My thesis is that
> it will fail.

Surely fails on Borland, for the same reason.

--
Aleksey Gurtovoy
MetaCommunications Engineering