I'm not actually sure if this is a gcc regression, or a bug in mpl, but the following code, which compiles under gcc 4.5, doesn't do so under gcc 4.6: #include <climits> #include <boost/mpl/int.hpp> typedef boost::mpl::int_<INT_MIN> Foo; Foo f; It produces the errors: /usr/local/include/boost/mpl/aux_/integral_wrapper.hpp: In instantiation of ‘mpl_::int_<-0x00000000080000000>’: test_test.cpp:8:27: instantiated from here /usr/local/include/boost/mpl/aux_/integral_wrapper.hpp:73:96: error: ‘2147483647’ is not a valid template argument for type ‘int’ because it is a non-constant expression /usr/local/include/boost/mpl/aux_/integral_wrapper.hpp:73:96: error: overflow in constant expression [-fpermissive] I've already created a trak ticket for this (#5268), but was wondering if anyone had any insights as to its cause and/or any workarounds. My guess is that its related to gcc rewriting parts of its constant folding code to support constexpr. -- Stirling Westrup Programmer, Entrepreneur. https://www.linkedin.com/e/fpf/77228 http://www.linkedin.com/in/swestrup http://technaut.livejournal.com http://sourceforge.net/users/stirlingwestrup