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, 1995, 1996, 1997, 1999, 2000, 2004
   4    Free Software Foundation, Inc.
   5    This file is part of the GNU C Library.
   6
   7    The GNU C Library is free software; you can redistribute it and/or
   8    modify it under the terms of the GNU Lesser General Public
   9    License as published by the Free Software Foundation; either
  10    version 2.1 of the License, or (at your option) any later version.
  11
  12    The GNU C Library is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15    Lesser General Public License for more details.
  16
  17    You should have received a copy of the GNU Lesser General Public
  18    License along with the GNU C Library; if not, write to the Free
  19    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  20    02111-1307 USA.  */
  21
  22 #ifndef _MATH_H
  23 # error "Never use <bits/huge_val.h> directly; include <math.h> instead."
  24 #endif
  25
  26 /* IEEE positive infinity (-HUGE_VAL is negative infinity).  */
  27
  28 #if __GNUC_PREREQ(3,3)
  29 # define HUGE_VAL       (__builtin_huge_val())
  30 #elif __GNUC_PREREQ(2,96)
  31 # define HUGE_VAL       (__extension__ 0x1.0p2047)
  32 #elif defined __GNUC__
  33
  34 # define HUGE_VAL \
  35   (__extension__                                                              \
  36    ((union { unsigned __l __attribute__((__mode__(__DI__))); double __d; })   \
  37     { __l: 0x7ff0000000000000ULL }).__d)
  38
  39 #else /* not GCC */
  40
  41 # include <endian.h>
  42
  43 typedef union { unsigned char __c[8]; double __d; } __huge_val_t;
  44
  45 # if __BYTE_ORDER == __BIG_ENDIAN
  46 #  define __HUGE_VAL_bytes      { 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 }
  47 # endif
  48 # if __BYTE_ORDER == __LITTLE_ENDIAN
  49 #  define __HUGE_VAL_bytes      { 0, 0, 0, 0, 0, 0, 0xf0, 0x7f }
  50 # endif
  51
  52 static __huge_val_t __huge_val = { __HUGE_VAL_bytes };
  53 # define HUGE_VAL       (__huge_val.__d)
  54
  55 #endif  /* GCC.  */