Hello List, I was using boost::filesystem previously in a project that built an executable but it has now grown and the requirements changed, and I now have to build a portion of the code as a library; preferably an so. Since I've started building code as a library I've been getting errors about invalid references to boost::filesystem. Here's how I'm building the library: $ g++ -DBOOST_ALL_NO_LIB -fPIC -lrt -lstdc++ -shared -pthread -lboost_system -lboost_thread -lboost_filesystem -L/usr/local/lib -ldl -lpthread -lstdc++ -lclang -o libomnis.so cout.o command_line_processor.o command_options_container.o commands_container.o command_base.o command_option_base.o command_option.o command_option_multi.o command_option_integer.o command_option_flag.o command_serve.o command_send.o command_help.o command_version.o register.o unsaved_file.o clang_parameters.o ustring_vector.o string_vector.o request_strings.o source_file.o reply.o omnisource.o omnis.o As you can see I've tried building it with (as well as without) the BOOST_ALL_NO_LIB macro defined. I then compile the main executable as given: $ g++ libomnis.so client.o omnis_command_line_processor.o request_handler.o request_handler_1.0.o request_parser.o server.o connection.o omnisource_loader.o omnis_app.o main.o -o omnis -pthread -lboost_system -lboost_thread -lboost_filesystem -L/usr/local/lib -ldl -lpthread -lstdc++ -lclang -L. -lomnis And this results in the following output: ./libomnis.so: undefined reference to `boost::filesystem2::detail::dir_itr_close(void*&, void*&)' ./libomnis.so: undefined reference to `boost::filesystem2::detail::dir_itr_first(void*&, void*&, std::string const&, std::string&, boost::filesystem2::file_status&, boost::filesystem2::file_status&)' ./libomnis.so: undefined reference to `boost::filesystem2::detail::dir_itr_increment(void*&, void*&, std::string&, boost::filesystem2::file_status&, boost::filesystem2::file_status&)' ./libomnis.so: undefined reference to `boost::filesystem2::detail::status_api(std::string const&, boost::system::error_code&)' ./libomnis.so: undefined reference to `boost::filesystem2::detail::not_found_error()' collect2: error: ld returned 1 exit status What am I missing here? PS: No errors occurred previously when I was just building the executable. -- Miguel