(Rearranging ...) On 11/28/2012 11:32 AM, Oliver Kowalke wrote:
Am 28.11.2012 19:45 schrieb "Eric Niebler" <eric@boostpro.com>:
On 11/28/2012 6:14 AM, Mathias Gaunard wrote:
On 28/11/12 08:42, Oliver Kowalke wrote:
Hello, clang (c++11 support) fails on code like:
BOOST_STATIC_ASSERT(( is_same< void, typename result_of< Fn() >::type > ::value));
with error:
no type named 'type' in 'boost::result_of<void (&())(X &)>' is_same< void, typename result_of< Fn() >::type > ::value)); ~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~**~~
Does Fn == void (&)(X&) or void (X&) ? I.e., is it a unary function type?
it's called inside a templated function: template< typename Fn > void g(BOOST_RV_RV( Fn) fn){ BOOST_STATIC_ASSERT(...) ....}
remove the reference from Fn (at least in C++11). I don't know what the actual type of Fn is in C++03.
Did my previous answer not fully address this issue? The function type void(&)(X&) cannot be called with 0 arguments, so a decltype-based result_of will have the behavior your observe. The old TR1-style result_of will give you void. At present, decltype-based result_of is only enabled for very recent clang builds. This explains the difference.
would function_traits<Fn>::result_type work better?
You are asking result_of to compute the result of calling a unary function that takes an X& with zero arguments. That's nonsensical. If you intend to call it with an X&, then ask it what the result is when called with an X&: boost::result_of< Fn(X&) >::type This should correctly report void regardless of whether result_of uses decltype or the TR1 result_of protocol. HTH, -- Eric Niebler BoostPro Computing http://www.boostpro.com