Martin Sebor wrote:
>Travis Vitek wrote:
>>
>>
[...]
>
>I can think of a couple of options that satisfy these. I'm not sure
>how palatable I find them yet, but I might get over their (initial)
>lack of appeal if the payoff is worth it. YMMV.
>
>One is to drop the cv specializations of the __rw_is_xxx traits and
>define the standard traits in terms of both remove_cv and the __rw
>traits, like so:
>
> template <class _TypeT>
> struct is_void:
> integral_constant<bool,
> _RW::__rw_is_void<typename
> _RW::__rw_remove_cv<_TypeT>::type>::value>
> { };
>
>or more concisely:
>
> template <class _TypeT>
> struct is_void:
> integral_constant<bool, _RWSTD_IS_VOID (_TypeT)::value>
> { };
>
>with _RWSTD_IS_VOID() being #defined like so:
>
> #define _RWSTD_IS_VOID(T) \
> _RW::__rw_is_void<typename _RW::__rw_remove_cv<T>::type>
>
>All internal code would always need to use _RWSTD_IS_VOID() and
>never _RW::__rw_is_void directly.
>
I think there is a problem with _RWSTD_IS_VOID() being defined like this
because it can't be used outside a template (because of the typename
keyword being used in the macro definition).
$ cat u.cpp && g++ u.cpp
namespace __rw {
template <class T>
struct __rw_remove_cv { typedef T type; };
template <class T>
struct __rw_is_void { enum { value = 0 }; };
template <>
struct __rw_is_void<void> { enum { value = 1 }; };
}
#define _RW __rw
#define _RWSTD_IS_VOID(T) \
_RW::__rw_is_void<typename _RW::__rw_remove_cv<T>::type>
int main ()
{
const bool b = _RWSTD_IS_VOID(void)::value;
return b == 0;
}
u.cpp: In function 'int main()':
u.cpp:23: error: using 'typename' outside of template
Travis
>
