--- /dev/null
+/* Checking macros for select functions.
+ Copyright (C) 2011-2018 Free Software Foundation, Inc.
+ This file is part of the GNU C Library.
+
+ The GNU C Library is free software; you can redistribute it and/or
+ modify it under the terms of the GNU Lesser General Public
+ License as published by the Free Software Foundation; either
+ version 2.1 of the License, or (at your option) any later version.
+
+ The GNU C Library is distributed in the hope that it will be useful,
+ but WITHOUT ANY WARRANTY; without even the implied warranty of
+ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ Lesser General Public License for more details.
+
+ You should have received a copy of the GNU Lesser General Public
+ License along with the GNU C Library; if not, see
+ <http://www.gnu.org/licenses/>. */
+
+#ifndef _SYS_SELECT_H
+# error "Never include <bits/select2.h> directly; use <sys/select.h> instead."
+#endif
+
+/* Helper functions to issue warnings and errors when needed. */
+extern long int __fdelt_chk (long int __d);
+extern long int __fdelt_warn (long int __d)
+ __warnattr ("bit outside of fd_set selected");
+#undef __FD_ELT
+#define __FD_ELT(d) \
+ __extension__ \
+ ({ long int __d = (d); \
+ (__builtin_constant_p (__d) \
+ ? (0 <= __d && __d < __FD_SETSIZE \
+ ? (__d / __NFDBITS) \
+ : __fdelt_warn (__d)) \
+ : __fdelt_chk (__d)); })