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

     1  /* `NAN' constant for IEEE 754 machines.
     2     Copyright (C) 1992-2016 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 _MATH_H
    20  #error "Never use <bits/nan.h> directly; include <math.h> instead."
    21  #endif
    22  
    23  /* IEEE Not A Number.  */
    24  
    25  #if __GNUC_PREREQ(3,3)
    26  
    27  #define NAN	(__builtin_nanf (""))
    28  
    29  #elif defined __GNUC__
    30  
    31  #define NAN \
    32    (__extension__							      \
    33     ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; })  \
    34      { __l: 0x7fc00000UL }).__d)
    35  
    36  #else
    37  
    38  #include <endian.h>
    39  
    40  #if __BYTE_ORDER == __BIG_ENDIAN
    41  #define __qnan_bytes		{ 0x7f, 0xc0, 0, 0 }
    42  #endif
    43  #if __BYTE_ORDER == __LITTLE_ENDIAN
    44  #define __qnan_bytes		{ 0, 0, 0xc0, 0x7f }
    45  #endif
    46  
    47  static union {
    48  	unsigned char __c[4];
    49  	float __d;
    50  } __qnan_union __attribute__ ((__unused__)) = {
    51  __qnan_bytes};
    52  
    53  #define NAN	(__qnan_union.__d)
    54  
    55  #endif				/* GCC.  */