I am trying to build a client program using Boost on MSVC8 with the "Disable Language Extensions" /Za compilation flag. visual.hpp contains the following code // disable Win32 API's if compiler extentions are // turned off: // #ifndef _MSC_EXTENSIONS # define BOOST_DISABLE_WIN32 #endif win32.hpp contains: #ifndef BOOST_DISABLE_WIN32 // WEK: Added #define BOOST_HAS_FTIME #define BOOST_WINDOWS 1 #endif So, the preprocessor defines BOOST_DISABLE_WIN32 and doesn't define BOOST_WINDOWS. This doesn't sound right, and causes problems with Boost.ASIO where the Windows header files are conditionally included using #if defined(BOOST_WINDOWS) || defined(__CYGWIN__) which clearly evaluates FALSE. I consider this a bug in the boost config compiler detection rather than the asio library. Has anyone compiled with /ZA on MSVC? Thanks -- Craig Craig Henderson <http://craighenderson.co.uk/> http://www.craighenderson.co.uk http://www.siteupdatenotification.com