lib/logf.c

   1 /* Natural logarithmic function.
   2    Copyright (C) 2011-2020 Free Software Foundation, Inc.
   3
   4    This program is free software: you can redistribute it and/or modify
   5    it under the terms of the GNU General Public License as published by
   6    the Free Software Foundation; either version 3 of the License, or
   7    (at your option) any later version.
   8
   9    This program is distributed in the hope that it will be useful,
  10    but WITHOUT ANY WARRANTY; without even the implied warranty of
  11    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12    GNU General Public License for more details.
  13
  14    You should have received a copy of the GNU General Public License
  15    along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
  16
  17 #include <config.h>
  18
  19 /* Specification.  */
  20 #include <math.h>
  21
  22 float
  23 logf (float x)
  24 #undef logf
  25 {
  26 #if HAVE_LOGF
  27   if (x <= 0.0f)
  28     {
  29       /* Work around the OSF/1 5.1 bug.  */
  30       if (x == 0.0f)
  31         /* Return -Infinity.  */
  32         return -1.0f / 0.0f;
  33       /* Work around the NetBSD 5.1 bug.  */
  34       else /* x < 0.0 */
  35         /* Return NaN.  */
  36         return 0.0f / 0.0f;
  37     }
  38   return logf (x);
  39 #else
  40   return (float) log ((double) x);
  41 #endif
  42 }