Re: [boost] [result_of] fails with clan (C++11)

Subject: Re: [boost] [result_of] fails with clan (C++11)
From: Oliver Kowalke (oliver.kowalke_at_[hidden])
Date: 2012-11-28 14:32:55

would function_traits<Fn>::result_type work better?
Am 28.11.2012 19:45 schrieb "Eric Niebler" <eric_at_[hidden]>:

> 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.
>
> --
> Eric Niebler
> BoostPro Computing
> http://www.boostpro.com
>
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