Greetings, I have a header file that includes both <boost/thread> and <boost/asio>, which results in the compilation errors below under cygwin. If I take out <boost/thread> then things are fine, except that I need it for my application :) I have "-D__USE_W32_SOCKETS -D_WIN32_WINNT=0x0501" in my compile flags, per the asio documentation. Taking them out appears to resolve the errors below, but causes other errors for asio. Has anyone else run into this problem and found a solution? -Brian In file included from /usr/include/cygwin/sys_time.h:13, from /usr/include/sys/time.h:27, from /usr/local/include/boost-1_38/boost/date_time/c_time.hpp:31, from /usr/local/include/boost-1_38/boost/date_time/microsec_time_clock.hpp:21, from /usr/local/include/boost-1_38/boost/thread/thread_time.hpp:9, from /usr/local/include/boost-1_38/boost/thread/locks.hpp:12, from /usr/local/include/boost-1_38/boost/thread/pthread/mutex.hpp:11, from /usr/local/include/boost-1_38/boost/thread/mutex.hpp:16, from /usr/local/include/boost-1_38/boost/thread/pthread/thread_data.hpp:12, from /usr/local/include/boost-1_38/boost/thread/thread.hpp:17, from /usr/local/include/boost-1_38/boost/thread.hpp:13, from chat.cpp:23: /usr/include/sys/select.h:31: error: `fd_set' has not been declared /usr/include/sys/select.h:31: error: `fd_set' has not been declared /usr/include/sys/select.h:31: error: `fd_set' has not been declared /usr/include/sys/select.h:33: error: `fd_set' has not been declared /usr/include/sys/select.h:33: error: `fd_set' has not been declared /usr/include/sys/select.h:33: error: `fd_set' has not been declared In file included from /usr/local/include/boost-1_38/boost/asio/detail/socket_types.hpp:79, from /usr/local/include/boost-1_38/boost/asio/detail/win_iocp_io_service_fwd.hpp:24, from /usr/local/include/boost-1_38/boost/asio/io_service.hpp:37, from /usr/local/include/boost-1_38/boost/asio/basic_io_object.hpp:20, from /usr/local/include/boost-1_38/boost/asio/basic_socket.hpp:24, from /usr/local/include/boost-1_38/boost/asio/basic_datagram_socket.hpp:25, from /usr/local/include/boost-1_38/boost/asio.hpp:20, from chat.cpp:30: /usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../include/w32api/winsock2.h:109: error: redefinition of `struct timeval' /usr/include/sys/time.h:16: error: previous definition of `struct timeval' /usr/lib/gcc/i686-pc-cygwin/3.4.4/../../../../include/w32api/winsock2.h:632: error: declaration of C function `int select(int, fd_set*, fd_set*, fd_set*, const timeval*)' conflicts with /usr/include/sys/select.h:31: error: previous declaration `int select(int, int*, int*, int*, timeval*)' here