Hi, I am using boost v1.34.1 and the "current" version of mingw. I got a problem (and solution) with the filesystem library: If the file convenience.hpp is included multiple times, mingw/gcc says: In function `ZN5boost10filesystem9extensionERKNS0_10basic_pathISsNS0_11path_traitsEEE':C:/Daten/Programme/Dev/boost_1_34_1/include/boost/filesystem/convenience.hpp:58: multiple definition of `boost::filesystem::extension(boost::filesystem::basic_path const&)' obj\Debug\Source\global.o:C:/Daten/Programme/Dev/boost_1_34_1/include/boost/filesystem/convenience.hpp:58: first defined here I can solve that (at least for me), if line 31 in convenience.hpp # define BOOST_FS_FUNC_STRING std::string is changed to # define BOOST_FS_FUNC_STRING inline std::string Another change I did to avoid an anoying warning is in line 45 boost::throw_exception( basic_filesystem_error<Path>( "boost::filesystem::create_directories", ph, -1 ) ); I changed the third parameter to 0, since it is unsigned. Have a nice day, Lennart