Re: [boost] [config] local types as template params

Subject: Re: [boost] [config] local types as template params
From: Mathias Gaunard (mathias.gaunard_at_[hidden])
Date: 2012-01-05 13:00:45

On 01/02/2012 10:58 AM, Lorenzo Caminiti wrote:
> Hello all,
>
> Is it possible to add a macro
> BOOST_CONFIG_LOCAL_TYPES_AS_TEMPLATE_PARAMS to Boost.Config to
> indicate if local types can be passed as template parameters?
>
> 1) Boost.Closure (formerly, Boost.Local) implements some optimizations
> when local types can be passed as template parameters.
> 2) C++11 always allows to pass local types as template parameters.
> 3) Local types cannot be passed as template parameters on C++03
> instead but some C++03 compilers MSVC 8 (and older?) allow it anyway.
>
> // If it is possible to pass local types (classes, etc) as template parameters.
> // This is not possible in pure C++03 but it is possible in some C++03
> // extensions (MSVC 8.0) and with C++11 (GCC>= 4.5.x -std=c++0x).
> #if (__GNUC__>  4 || (__GNUC__ == 4&&  __GNUC_MINOR__>  4))&&  \
>          defined(__GXX_EXPERIMENTAL_CXX0X__)
>      // From GCC 4.5.x when -std=c++0x specified.
> #   define BOOST_LOCAL_TYPES_AS_TEMPLATE_PARAMS
> #elif defined(_MSC_VER)
>      // For (all?) MSVC (tested on MVSC 8.0).
> #   define BOOST_LOCAL_TYPES_AS_TEMPLATE_PARAMS
> #endif

Boost.Config is not organized like that, it's per compiler.
the name should also be BOOST_NO_LOCAL_TYPES_AS_TEMPLATE_PARAMS.

Finally this seems incomplete, local types as template params used to 
work in C++03 with older versions of GCC too.
It does indeed work for all versions of MSVC AFAIK.