misc/bits/select2.h

   1 /* Checking macros for select functions.
   2    Copyright (C) 2011-2017 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #ifndef _SYS_SELECT_H
  20 # error "Never include <bits/select2.h> directly; use <sys/select.h> instead."
  21 #endif
  22
  23 /* Helper functions to issue warnings and errors when needed.  */
  24 extern long int __fdelt_chk (long int __d);
  25 extern long int __fdelt_warn (long int __d)
  26   __warnattr ("bit outside of fd_set selected");
  27 #undef __FD_ELT
  28 #define __FD_ELT(d) \
  29   __extension__                                                             \
  30   ({ long int __d = (d);                                                    \
  31      (__builtin_constant_p (__d)                                            \
  32       ? (0 <= __d && __d < __FD_SETSIZE                                     \
  33          ? (__d / __NFDBITS)                                                \
  34          : __fdelt_warn (__d))                                              \
  35       : __fdelt_chk (__d)); })