modernc.org/cc@v1.0.1/v2/headers/linux_arm/usr/include/arm-linux-gnueabihf/bits/huge_val.h (about)

     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) 1992-2016 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 {
    42  	unsigned char __c[8];
    43  	double __d;
    44  } __huge_val_t;
    45  
    46  #if __BYTE_ORDER == __BIG_ENDIAN
    47  #define __HUGE_VAL_bytes	{ 0x7f, 0xf0, 0, 0, 0, 0, 0, 0 }
    48  #endif
    49  #if __BYTE_ORDER == __LITTLE_ENDIAN
    50  #define __HUGE_VAL_bytes	{ 0, 0, 0, 0, 0, 0, 0xf0, 0x7f }
    51  #endif
    52  
    53  static __huge_val_t __huge_val = { __HUGE_VAL_bytes };
    54  
    55  #define HUGE_VAL	(__huge_val.__d)
    56  
    57  #endif				/* GCC.  */