[boost] [config] local types as template params

Subject: [boost] [config] local types as template params
From: Lorenzo Caminiti (lorcaminiti_at_[hidden])
Date: 2012-01-02 04:58:53

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

All, can you please try to compile the following example on different
compilers/versions and let me know the outcome? If this example
compiles successfully then the specific compiler supports local types
as template parameters:

#include <algorithm>
#include <iostream>

int main() {
    struct s {
        void operator()(int x) {
            std::cout << x << std::endl;
        }
    } l;

    int nums[] = {1, 2, 3};
    std::for_each(nums, nums + 3, l);

    return 0;
}

For example, this compiles on GCC >= 4.5.x w/ C++0x extensions enabled
and on MSVC 8.0- does it compile on all MSVC versions?

Thanks.
--Lorenzo