math/w_scalb_compat.c

   1 /* Copyright (C) 2011-2017 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3    Contributed by Ulrich Drepper <drepper@gmail.com>, 2011.
   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 #include <errno.h>
  20 #include <math.h>
  21 #include <math_private.h>
  22 #include <math-svid-compat.h>
  23
  24
  25 #if LIBM_SVID_COMPAT
  26 static double
  27 __attribute__ ((noinline))
  28 sysv_scalb (double x, double fn)
  29 {
  30   double z = __ieee754_scalb (x, fn);
  31
  32   if (__glibc_unlikely (isinf (z)))
  33     {
  34       if (isfinite (x))
  35         return __kernel_standard (x, fn, 32); /* scalb overflow */
  36       else
  37         __set_errno (ERANGE);
  38     }
  39   else if (__builtin_expect (z == 0.0, 0) && z != x)
  40     return __kernel_standard (x, fn, 33); /* scalb underflow */
  41
  42   return z;
  43 }
  44 #endif
  45
  46
  47 /* Wrapper scalb */
  48 double
  49 __scalb (double x, double fn)
  50 {
  51 #if LIBM_SVID_COMPAT
  52   if (__glibc_unlikely (_LIB_VERSION == _SVID_))
  53     return sysv_scalb (x, fn);
  54   else
  55 #endif
  56     {
  57       double z = __ieee754_scalb (x, fn);
  58
  59       if (__glibc_unlikely (!isfinite (z) || z == 0.0))
  60         {
  61           if (isnan (z))
  62             {
  63               if (!isnan (x) && !isnan (fn))
  64                 __set_errno (EDOM);
  65             }
  66           else if (isinf (z))
  67             {
  68               if (!isinf (x) && !isinf (fn))
  69                 __set_errno (ERANGE);
  70             }
  71           else
  72             {
  73               /* z == 0.  */
  74               if (x != 0.0 && !isinf (fn))
  75                 __set_errno (ERANGE);
  76             }
  77         }
  78       return z;
  79     }
  80 }
  81 weak_alias (__scalb, scalb)
  82 #ifdef NO_LONG_DOUBLE
  83 strong_alias (__scalb, __scalbl)
  84 weak_alias (__scalb, scalbl)
  85 #endif