sysdeps/ieee754/bits/huge_val.h

   1 /* `HUGE_VAL' constant for IEEE 754 machines (where it is infinity).
   2    Used by <stdlib.h> and <math.h> functions for overflow.
   3    Copyright (C) 1992-2014 Free Software Foundation, Inc.
   4    This file is part of the GNU C Library.
   5
   6    The GNU C Library is free software; you can redistribute it and/or
   7    modify it under the terms of the GNU Lesser General Public
   8    License as published by the Free Software Foundation; either
   9    version 2.1 of the License, or (at your option) any later version.
  10
  11    The GNU C Library is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14    Lesser General Public License for more details.
  15
  16    You should have received a copy of the GNU Lesser General Public
  17    License along with the GNU C Library; if not, see
  18    <http://www.gnu.org/licenses/>.  */
  19
  20 #ifndef _MATH_H
  21 # error "Never use <bits/huge_val.h> directly; include <math.h> instead."
  22 #endif
  23
  24 /* IEEE positive infinity (-HUGE_VAL is negative infinity).  */
  25
  26 #if __GNUC_PREREQ(3,3)
  27 # define HUGE_VAL       (__builtin_huge_val())
  28 #elif __GNUC_PREREQ(2,96)
  29 # define HUGE_VAL       (__extension__ 0x1.0p2047)
  30 #elif defined __GNUC__
  31
  32 # define HUGE_VAL \
  33   (__extension__                                                              \
  34    ((union { unsigned __l __attribute__((__mode__(__DI__))); double __d; })   \
  35     { __l: 0x7ff0000000000000ULL }).__d)
  36
  37 #else /* not GCC */
  38
  39 # include <endian.h>
  40
  41 typedef union { unsigned char __c[8]; double __d; } __huge_val_t;
  42
  43 # if __BYTE_ORDER == __BIG_ENDIAN
  44 #  define __HUGE_VAL_bytes      { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 }
  45 # endif
  46 # if __BYTE_ORDER == __LITTLE_ENDIAN
  47 #  define __HUGE_VAL_bytes      { 0, 0, 0, 0, 0, 0, 0xf0, 0x7f }
  48 # endif
  49
  50 static __huge_val_t __huge_val = { __HUGE_VAL_bytes };
  51 # define HUGE_VAL       (__huge_val.__d)
  52
  53 #endif  /* GCC.  */