Falling back to select_io_watcher when target OS(NT < 6.0) not support it

Author: halx99

yasio/compiler/feature_test.hpp

@@ -121,6 +121,13 @@ SOFTWARE.
 
 /// Tests multiplex io model of current OS
 
+// poll
+#if !defined(_WIN32) || NTDDI_VERSION >= NTDDI_VISTA
+#  define YASIO__HAS_POLL 1
+#else
+#  define YASIO__HAS_POLL 0
+#endif
+
 // ppoll
 #if defined(__linux__) && !defined(__ANDROID__) || (defined(__ANDROID_API__) && __ANDROID_API__ >= 21)
 #  define YASIO__HAS_PPOLL 1

yasio/io_watcher.hpp

@@ -17,7 +17,12 @@
 #elif YASIO__HAS_EVPORT && defined(YASIO_ENABLE_HPERF_IO)
 #  include "yasio/impl/evport_io_watcher.hpp"
 #elif !defined(YASIO_DISABLE_POLL)
-#  include "yasio/impl/poll_io_watcher.hpp"
+#  if YASIO__HAS_POLL
+#    include "yasio/impl/poll_io_watcher.hpp"
+#  else
+#    pragma message("Falling back to select_io_watcher due to target OS(NT < 6.0) not support it")
+#    include "yasio/impl/select_io_watcher.hpp"
+#  endif
 #else
 #  include "yasio/impl/select_io_watcher.hpp"
 #endif
@@ -33,7 +38,7 @@ using io_watcher = kqueue_io_watcher;
 using io_watcher = epoll_io_watcher;
 #elif defined(YASIO__EVPORT_IO_WATCHER_HPP)
 using io_watcher = evport_io_watcher;
-#elif !defined(YASIO_DISABLE_POLL)
+#elif !defined(YASIO_DISABLE_POLL) && YASIO__HAS_POLL
 using io_watcher = poll_io_watcher;
 #else
 using io_watcher = select_io_watcher;