[Boost-users] Re: MPL Issue in apply.hpp in CVS

From: David Abrahams (dave_at_[hidden])
Date: 2004-01-25 09:24:29

"Martin Ecker" <martin.ecker_at_[hidden]> writes:

> Hello,
>
> I wanted to use boost::variant, so I got the Boost libraries
> from CVS. While developing a small test program I discovered
> an issue in the MPL header file apply.hpp that prevented
> successful compilation on MSVC 7.1. In particular, starting
> on line 245 in boost/mpl/apply.hpp it says
>
> // ISO98 C++, with minor concession to vc7
>
> template<
>       typename F, AUX_APPLY_N_PARAMS(i, typename T)
>     >
> struct BOOST_PP_CAT(apply,i)
> {
>     // Metafunction forwarding confuses vc7
>     typedef typename F::template apply<
>        AUX_APPLY_N_PARAMS(i, T)
>     >::type
>         
>     BOOST_MPL_AUX_LAMBDA_SUPPORT(
>           BOOST_PP_INC(i)
>         , BOOST_PP_CAT(apply,i)
>         , (F, AUX_APPLY_N_PARAMS(i,T))
>         )
> };
>
> The first typedef in that struct should be
>
>     // Metafunction forwarding confuses vc7
>     typedef typename F::template apply<
>        AUX_APPLY_N_PARAMS(i, T)
>     >::type type;

Thanks.  This bug has gone unnoticed since October!  But it's a little
bit strange that you encountered it at all, since your compiler should
be seeing the preprocessed header at
boost/mpl/aux_/preprocessed/plain/apply.hpp (unless you've got
BOOST_MPL_NO_PREPROCESSED_HEADERS defined, of course).

-- 
Dave Abrahams
Boost Consulting
www.boost-consulting.com