I'm trying to use the Boost Test framework for unit testing in asio but it doesn't work for Win9x/ME targets without a minor fix. The problem is due to boost/test/impl/execution_monitor.ipp only checking for _WIN32_WINNT, when the #define for Win9x/ME is _WIN32_WINDOWS. I had to make the following change to get it to work: @@ -55,7 +55,7 @@ # define BOOST_MS_STRUCTURED_EXCEPTION_HANDLING -# ifndef _WIN32_WINNT +# if !defined(_WIN32_WINNT) && !defined(_WIN32_WINDOWS) # ifdef _WINBASE_ # warning Debugger check disabled. Either define _WIN32_WINNT or include Boost.Test header in front of winbase.h # else I also encountered this as an error, rather than a warning as intended, because #warning is not supported by MSVC. It should probably use #pragma message("...") instead. Cheers, Chris