lib/nan.h

   1 /* Macros for quiet not-a-number.
   2    Copyright (C) 2007-2024 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 #ifndef _GL_NAN_H
  18 #define _GL_NAN_H
  19
  20
  21 /* IBM z/OS supports both hexadecimal and IEEE floating-point formats. The
  22    former does not support NaN and its isnan() implementation returns zero
  23    for all values.  */
  24 #if defined __MVS__ && defined __IBMC__ && !defined __BFP__
  25 # error "NaN is not supported with IBM's hexadecimal floating-point format; please re-compile with -qfloat=ieee"
  26 #endif
  27
  28 /* NaNf () returns a 'float' not-a-number.  */
  29
  30 /* The Compaq (ex-DEC) C 6.4 compiler and the Microsoft MSVC 9 compiler choke
  31    on the expression 0.0 / 0.0.  The IBM XL C compiler on z/OS complains.
  32    PGI 16.10 complains.  clang 13 on mips64 does incorrect constant-folding.  */
  33 #if (defined __DECC || defined _MSC_VER \
  34      || (defined __MVS__ && defined __IBMC__) \
  35      || defined __PGI \
  36      || defined __mips__)
  37 static float
  38 NaNf ()
  39 {
  40   static float volatile zero = 0.0f;
  41   return zero / zero;
  42 }
  43 #else
  44 # define NaNf() (0.0f / 0.0f)
  45 #endif
  46
  47
  48 /* NaNd () returns a 'double' not-a-number.  */
  49
  50 /* The Compaq (ex-DEC) C 6.4 compiler and the Microsoft MSVC 9 compiler choke
  51    on the expression 0.0 / 0.0.  The IBM XL C compiler on z/OS complains.
  52    PGI 16.10 complains.  clang 13 on mips64 does incorrect constant-folding.  */
  53 #if (defined __DECC || defined _MSC_VER \
  54      || (defined __MVS__ && defined __IBMC__) \
  55      || defined __PGI \
  56      || defined __mips__)
  57 static double
  58 NaNd ()
  59 {
  60   static double volatile zero = 0.0;
  61   return zero / zero;
  62 }
  63 #else
  64 # define NaNd() (0.0 / 0.0)
  65 #endif
  66
  67
  68 /* NaNl () returns a 'long double' not-a-number.  */
  69
  70 /* On Irix 6.5, gcc 3.4.3 can't compute compile-time NaN, and needs the
  71    runtime type conversion.
  72    The Microsoft MSVC 9 compiler chokes on the expression 0.0L / 0.0L.
  73    The IBM XL C compiler on z/OS complains.
  74    PGI 16.10 complains.
  75    Avoid possible incorrect constant-folding on mips.  */
  76 #ifdef __sgi
  77 static long double NaNl ()
  78 {
  79   double zero = 0.0;
  80   return zero / zero;
  81 }
  82 #elif (defined _MSC_VER \
  83        || (defined __MVS__ && defined __IBMC__) \
  84        || defined __PGI \
  85        || defined __mips__)
  86 static long double
  87 NaNl ()
  88 {
  89   static long double volatile zero = 0.0L;
  90   return zero / zero;
  91 }
  92 #else
  93 # define NaNl() (0.0L / 0.0L)
  94 #endif
  95
  96
  97 #endif /* _GL_NAN_H */