Hi, Is there any particular reason that type_with_alignment does not support alignment more than 32 on gcc? I am trying to create an unordered_map of objects that are aligned to cache line size (64bytes) and it fails in type_with_alignment. This small example shows it: #include <boost/tr1/unordered_map.hpp> struct __attribute__((aligned(64)) A { int i; }; int main() { std::tr1::unordered_map<int, A> umap; umap[0] = A(); return 0; } In file included from /usr/local/boost/boost_1.48/include/boost/aligned_storage.hpp:21:0, from /usr/local/boost/boost_1.48/include/boost/type_traits/aligned_storage.hpp:11, from /usr/local/boost/boost_1.48/include/boost/unordered/detail/buckets.hpp:17, from /usr/local/boost/boost_1.48/include/boost/unordered/detail/table.hpp:10, from /usr/local/boost/boost_1.48/include/boost/unordered/detail/equivalent.hpp:14, from /usr/local/boost/boost_1.48/include/boost/unordered/unordered_map.hpp:18, from /usr/local/boost/boost_1.48/include/boost/unordered_map.hpp:16, from /usr/local/boost/boost_1.48/include/boost/tr1/unordered_map.hpp:21, from test.cc:1: /usr/local/boost/boost_1.48/include/boost/type_traits/type_with_alignment.hpp: In instantiation of ‘boost::detail::type_with_alignment_imp<64ul>’: /usr/local/boost/boost_1.48/include/boost/type_traits/type_with_alignment.hpp:216:7: instantiated from ‘boost::type_with_alignment<64ul>’ /usr/local/boost/boost_1.48/include/boost/mpl/eval_if.hpp:60:31: instantiated from ‘boost::mpl::eval_if_c<false, boost::mpl::identity<boost::detail::max_align>, boost::type_with_alignment<64ul> >’ /usr/local/boost/boost_1.48/include/boost/aligned_storage.hpp:55:21: instantiated from ‘boost::detail::aligned_storage::aligned_storage_imp<128ul, 64ul>::data_t’ /usr/local/boost/boost_1.48/include/boost/aligned_storage.hpp:56:7: instantiated from ‘boost::detail::aligned_storage::aligned_storage_imp<128ul, 64ul>’ /usr/local/boost/boost_1.48/include/boost/aligned_storage.hpp:73:7: instantiated from ‘boost::aligned_storage<128ul, 64ul>’ /usr/local/boost/boost_1.48/include/boost/unordered/detail/table.hpp:281:59: instantiated from ‘boost::unordered::detail::value_base<std::pair<const int, A> >’ /usr/local/boost/boost_1.48/include/boost/unordered/detail/unique.hpp:47:12: instantiated from ‘boost::unordered::detail::ptr_node<std::pair<const int, A> >’ /usr/local/boost/boost_1.48/include/boost/unordered/detail/unique.hpp:332:40: instantiated from ‘boost::unordered::detail::table_impl<Types>::value_type& boost::unordered::detail::table_impl<Types>::operator[](const key_type&) [with Types = boost::unordered::detail::map<std::allocator<std::pair<const int, A> >, int, boost::hash<int>, std::equal_to<int> >, boost::unordered::detail::table_impl<Types>::value_type = std::pair<const int, A>, boost::unordered::detail::table_impl<Types>::key_type = int]’ /usr/local/boost/boost_1.48/include/boost/unordered/unordered_map.hpp:1007:26: instantiated from ‘boost::unordered::unordered_map<K, T, H, P, A>::mapped_type& boost::unordered::unordered_map<K, T, H, P, A>::operator[](const key_type&) [with K = int, T = A, H = boost::hash<int>, P = std::equal_to<int>, A = std::allocator<std::pair<const int, A> >, boost::unordered::unordered_map<K, T, H, P, A>::mapped_type = A, boost::unordered::unordered_map<K, T, H, P, A>::key_type = int]’ test.cc:11:9: instantiated from here /usr/local/boost/boost_1.48/include/boost/type_traits/type_with_alignment.hpp:206:1: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’ /usr/local/boost/boost_1.48/include/boost/type_traits/type_with_alignment.hpp:207:1: error: invalid application of ‘sizeof’ to incomplete type ‘boost::STATIC_ASSERTION_FAILURE<false>’ Is there any easy way to avoid this problem? Thanks