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 /usr/local/include/boost/fusion/algorithm/iteration/for_each.hpp:32:9: error: no matching function for call to 'for_each(boost::fusion::vector2<double, double>&, const mace::rpc::detail::unpack_sequence<mace::rpc::function_filter<mace::rpc::connection<mace::rpc::json::io> > >&, boost::fusion::detail::fusion_category_of<boost::fusion::vector2<double, double> >::type)' /usr/local/include/boost/fusion/algorithm/iteration/for_each.hpp:32:9: note: candidate is: In file included from /usr/local/include/boost/fusion/algorithm/iteration/for_each.hpp:11:0, from /usr/local/include/boost/fusion/algorithm/iteration.hpp:12, from /usr/local/include/boost/fusion/algorithm.hpp:10, from /Users/dlarimer/projects/mace/libs/rpc/include/mace/rpc/json/io.hpp:13, from /Users/dlarimer/projects/mace/libs/rpc/include/mace/rpc/json/tcp/server.hpp:4, from /Users/dlarimer/projects/mace/libs/rpc/examples/json_tcps.cpp:1: /usr/local/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:130:5: note: template<class Sequence, class F> void boost::fusion::detail::for_each(Sequence&, const F&, mpl_::false_) /usr/local/include/boost/fusion/algorithm/iteration/detail/for_each.hpp:130:5: note: template argument deduction/substitution failed: In file included from /usr/local/include/boost/fusion/algorithm/iteration.hpp:12:0, from /usr/local/include/boost/fusion/algorithm.hpp:10, from /Users/dlarimer/projects/mace/libs/rpc/include/mace/rpc/json/io.hpp:13, from /Users/dlarimer/projects/mace/libs/rpc/include/mace/rpc/json/tcp/server.hpp:4, from /Users/dlarimer/projects/mace/libs/rpc/examples/json_tcps.cpp:1: /usr/local/include/boost/fusion/algorithm/iteration/for_each.hpp:32:9: note: cannot convert 'boost::fusion::detail::fusion_category_of<boost::fusion::vector2<double, double> >::type()' (type 'boost::fusion::detail::fusion_category_of<boost::fusion::vector2<double, double> >::type {aka boost::fusion::random_access_traversal_tag}') to type 'mpl_::false_ {aka mpl_::bool_<false>}'