Given: // cp.cpp #include <boost/filesystem.hpp> int main( int argc, char** argv ) { if( argc < 3 ) return -1; boost::filesystem::copy_file( argv[1], argv[2] ); return 0; } g++ -o cp cp.cpp -std=c++0x -I /usr/local/include /usr/local/lib/libboost_filesystem.a /usr/local/lib/libboost_system.a Undefined symbols for architecture x86_64: "boost::filesystem3::detail::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&, boost::filesystem3::copy_option, boost::system::error_code*)", referenced from: boost::filesystem3::copy_file(boost::filesystem3::path const&, boost::filesystem3::path const&) in ccUAyvBD.o ld: symbol(s) not found for architecture x86_64 collect2: error: ld returned 1 exit status If I remove the -std=c++0x flag then it links just fine. g++ --version g++ (MacPorts gcc47 4.7.0_3) 4.7.0 Copyright (C) 2012 Free Software Foundation, Inc. This is free software; see the source for copying conditions. There is NO warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. Dan