+#if !_LIBC
+/* Return non-zero if FD is open. */
+static inline int
+is_open (int fd)
+{
+# if (defined _WIN32 || defined __WIN32__) && ! defined __CYGWIN__
+ /* On Win32: The initial state of unassigned standard file descriptors is
+ that they are open but point to an INVALID_HANDLE_VALUE. There is no
+ fcntl, and the gnulib replacement fcntl does not support F_GETFL. */
+ return (HANDLE) _get_osfhandle (fd) != INVALID_HANDLE_VALUE;
+# else
+# ifndef F_GETFL
+# error Please port fcntl to your platform
+# endif
+ return 0 <= fcntl (fd, F_GETFL);
+# endif
+}
+#endif
+