Re: [boost] [fusion] for_each on gcc 4.7

Subject: Re: [boost] [fusion] for_each on gcc 4.7
From: Daniel Larimer (dlarimer_at_[hidden])
Date: 2012-06-20 22:00:56

On Jun 20, 2012, at 9:57 PM, Daniel Larimer wrote:

> On Jun 20, 2012, at 7:36 PM, Joel de Guzman wrote:
> 
>> On 6/20/2012 1:37 PM, Daniel Larimer wrote:
>>> I recently attempted to update to gcc 4.7 and code that compiled with 4.5.3 broke.
>>> 
>>> It appears that boost::fusion expects boost::fusion::random_access_traversal_tag to implicitly cast to mpl::bool_<false>.
>>> 
>>> Switching the 3rd argument from mpl::bool_<false>  to an extra template arg (that was ignored), seems to fix the compilation errors.
>>> 
>>> Compiled with std=c++11
>> 
>> Do you have a minimal test case?
> 
> #include <boost/fusion/container/vector.hpp>
> #include <boost/fusion/algorithm.hpp>
> #include <boost/fusion/include/make_vector.hpp>
> 
> struct visitor {
>  template<typename T>
>  void operator()( T t )const{}
> };
> 
> int main() {
>   visitor v;
>   boost::fusion::for_each( boost::fusion::make_vector(5,6.6), v );
>   return 0;
> }
> 
I could get things to compile by editing boost/fusion/algorithm/iteration/detail/for_each.hpp and changing the last parameter to Ty.   It appears that parameter was ignored anyway and that we didn't care about the type.

    template <typename Sequence, typename F, typename Ty>
    inline void
    for_each(Sequence& seq, F const& f, Ty) // unsegmented implementation
    {
        detail::for_each_dispatch(seq, f, typename traits::category_of<Sequence>::type());
    }

>> 
>> Regards,
>> -- 
>> Joel de Guzman
>> http://www.boostpro.com
>> http://boost-spirit.com
>> 
>> 
>> 
>> 
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>