text: /* Return 1 if argument is a NaN, else 0.
     Copyright (C) 2007-2020 Free Software Foundation, Inc.
     This file is part of the GNU C Library.
  
     The GNU C Library is free software; you can redistribute it and/or
     modify it under the terms of the GNU Lesser General Public
     License as published by the Free Software Foundation; either
     version 2.1 of the License, or (at your option) any later version.
  
     The GNU C Library is distributed in the hope that it will be useful,
     but WITHOUT ANY WARRANTY; without even the implied warranty of
     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
     Lesser General Public License for more details.
  
     You should have received a copy of the GNU Lesser General Public
     License along with the GNU C Library.  If not, see
     <https://www.gnu.org/licenses/>.  */
  
  /* Ugly kludge to avoid declarations.  */
  #define __isnanf	not___isnanf
  #define isnanf		not_isnanf
  #define __GI___isnanf	not__GI___isnanf
  
  #include <math.h>
  #include <math_private.h>
  #include <math_ldbl_opt.h>
  
  #undef __isnanf
  #undef isnanf
  #undef __GI___isnanf
  
  int
  __isnan (double x)
  {
    uint64_t ix;
    EXTRACT_WORDS64 (ix, x);
    return ix * 2 > 0xffe0000000000000ul;
  }
  
  hidden_def (__isnan)
  weak_alias (__isnan, isnan)
  
  /* It turns out that the 'double' version will also always work for
     single-precision.  */
  strong_alias (__isnan, __isnanf)
  weak_alias (__isnan, isnanf)
  
  /* ??? GCC 4.8 fails to look through chains of aliases with asm names
     attached.  Work around this for now.  */
  hidden_ver (__isnan, __isnanf)
  
  #ifdef NO_LONG_DOUBLE
  strong_alias (__isnan, __isnanl)
  weak_alias (__isnan, isnanl)
  #endif
  #if LONG_DOUBLE_COMPAT(libc, GLIBC_2_0)
  compat_symbol (libc, __isnan, __isnanl, GLIBC_2_0);
  compat_symbol (libc, isnan, isnanl, GLIBC_2_0);
  #endif
  