I was going through recent Boost.Spirit changes and I was surprised to see this code: #if (defined(BOOST_MSVC) && (BOOST_MSVC < 1310)) \ || (defined(__BORLANDC__) && (__BORLANDC__ <= 0x570)) \ || (defined(__GNUC__) && (__GNUC__ < 3)) \ || (defined(__GNUC__) && (__GNUC__ == 3) && (__GNUC_MINOR__ < 1)) # error "Compiler not supported. See note in " #else // Pass... Compiler supported. #endif modified into this code: #if (defined(__BORLANDC__) && (__BORLANDC__ <= 0x570)) # error "Compiler not supported. See note in " #else // Pass... Compiler supported. #endif The whole point of the check is to detect unsupported compilers. It seems the modernization changes do not take into account the context in which they are done. To Stephen Kelly: I would like to suggest going over your modernization commits looking for unwanted changes like this one, and reverting them. I have already revisited your modifications to Boost.Spirit and found all changes but the one I mentioned to be valid ones (thank you for those!). Regards, -- Agustín K-ballo Bergé.- http://talesofcpp.fusionfenix.com