math/s_nan.c

   1 /* Return quiet nan.
   2    Copyright (C) 1997-2013 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4    Contributed by Ulrich Drepper <drepper@cygnus.com>, 1997.
   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 #include <math.h>
  21 #include <stdio.h>
  22 #include <stdlib.h>
  23 #include <string.h>
  24 #include <ieee754.h>
  25
  26
  27 #undef __nan
  28 double
  29 __nan (const char *tagp)
  30 {
  31   if (tagp[0] != '\0')
  32     {
  33       char buf[6 + strlen (tagp)];
  34       sprintf (buf, "NAN(%s)", tagp);
  35       return strtod (buf, NULL);
  36     }
  37
  38   return NAN;
  39 }
  40 weak_alias (__nan, nan)
  41 #ifdef NO_LONG_DOUBLE
  42 strong_alias (__nan, __nanl)
  43 weak_alias (__nan, nanl)
  44 #endif