math/w_scalb_compat.c

   1 /* Copyright (C) 2011-2023 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    The GNU C Library 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 GNU
  12    Lesser General Public License for more details.
  13
  14    You should have received a copy of the GNU Lesser General Public
  15    License along with the GNU C Library; if not, see
  16    <https://www.gnu.org/licenses/>.  */
  17
  18 #include <errno.h>
  19 #include <math.h>
  20 #include <math_private.h>
  21 #include <math-svid-compat.h>
  22
  23
  24 #if LIBM_SVID_COMPAT
  25 static double
  26 __attribute__ ((noinline))
  27 sysv_scalb (double x, double fn)
  28 {
  29   double z = __ieee754_scalb (x, fn);
  30
  31   if (__glibc_unlikely (isinf (z)))
  32     {
  33       if (isfinite (x))
  34         return __kernel_standard (x, fn, 32); /* scalb overflow */
  35       else
  36         __set_errno (ERANGE);
  37     }
  38   else if (__builtin_expect (z == 0.0, 0) && z != x)
  39     return __kernel_standard (x, fn, 33); /* scalb underflow */
  40
  41   return z;
  42 }
  43
  44
  45 /* Wrapper scalb */
  46 double
  47 __scalb (double x, double fn)
  48 {
  49   if (__glibc_unlikely (_LIB_VERSION == _SVID_))
  50     return sysv_scalb (x, fn);
  51   else
  52     {
  53       double z = __ieee754_scalb (x, fn);
  54
  55       if (__glibc_unlikely (!isfinite (z) || z == 0.0))
  56         {
  57           if (isnan (z))
  58             {
  59               if (!isnan (x) && !isnan (fn))
  60                 __set_errno (EDOM);
  61             }
  62           else if (isinf (z))
  63             {
  64               if (!isinf (x) && !isinf (fn))
  65                 __set_errno (ERANGE);
  66             }
  67           else
  68             {
  69               /* z == 0.  */
  70               if (x != 0.0 && !isinf (fn))
  71                 __set_errno (ERANGE);
  72             }
  73         }
  74       return z;
  75     }
  76 }
  77 weak_alias (__scalb, scalb)
  78 # ifdef NO_LONG_DOUBLE
  79 strong_alias (__scalb, __scalbl)
  80 weak_alias (__scalb, scalbl)
  81 # endif
  82 #endif