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- #ifndef _MATH_H
- # error "Never use <bits/nan.h> directly; include <math.h> instead."
- #endif
- #if __GNUC_PREREQ(3,3)
- # define NAN (__builtin_nanf (""))
- #elif defined __GNUC__
- # define NAN \
- (__extension__ \
- ((union { unsigned __l __attribute__ ((__mode__ (__SI__))); float __d; }) \
- { __l: 0x7fc00000UL }).__d)
- #else
- # include <endian.h>
- # if __BYTE_ORDER == __BIG_ENDIAN
- # define __qnan_bytes { 0x7f, 0xc0, 0, 0 }
- # endif
- # if __BYTE_ORDER == __LITTLE_ENDIAN
- # define __qnan_bytes { 0, 0, 0xc0, 0x7f }
- # endif
- static union { unsigned char __c[4]; float __d; } __qnan_union
- __attribute__ ((__unused__)) = { __qnan_bytes };
- # define NAN (__qnan_union.__d)
- #endif
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