new module 'isnanl-nolibm'

[Bruno Haible]

Hi,

printf also needs to output long double numbers... so it needs an isnanl()
function as well. Like for isnan(), having it defined in libm (OSF/1,
Solaris) doesn't help.

2007-02-24  Bruno Haible  <address@hidden>

        * modules/isnanl-nolibm: New file.
        * lib/isnanl.h: New file.
        * lib/isnanl.c: New file.
        * m4/isnanl.m4: New file.

================================ modules/isnanl-nolibm ========================
Description:
isnanl() function: test for NaN, without requiring libm.

Files:
lib/isnanl.h
lib/isnanl.c
m4/isnanl.m4
m4/longdouble.m4

Depends-on:

configure.ac:
gl_FUNC_ISNANL_NO_LIBM

Makefile.am:

Include:
#if HAVE_LONG_DOUBLE
# include "isnan.h"
#endif

License:
LGPL

Maintainer:
Bruno Haible

================================ lib/isnanl.h =================================
/* Test for NaN that does not need libm.
   Copyright (C) 2007 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

#if HAVE_ISNANL_IN_LIBC
/* Get declaration of isnanl.  */
# include <math.h>
#else
/* Test whether X is a NaN.  */
# undef isnanl
# define isnanl rpl_isnanl
extern int isnanl (long double x);
#endif
================================ lib/isnanl.c =================================
/* Test for NaN that does not need libm.
   Copyright (C) 2007 Free Software Foundation, Inc.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2, or (at your option)
   any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License along
   with this program; if not, write to the Free Software Foundation,
   Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.  */

/* Written by Bruno Haible <address@hidden>, 2007.  */

#include <config.h>

#include <float.h>
#include <string.h>

#define LDBL_EXP_MASK ((LDBL_MAX_EXP - LDBL_MIN_EXP) | 7)

#define NWORDS \
  ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
typedef union { long double value; unsigned int word[NWORDS]; }
        memory_long_double;

int
rpl_isnanl (long double x)
{
#if defined LDBL_EXPBIT0_WORD && defined LDBL_EXPBIT0_BIT
  /* Be careful to not do any floating-point operation on x, such as x == x,
     because x may be a signalling NaN.  */
  static memory_long_double nan = { 0.0L / 0.0L };
  static long double plus_inf = 1.0L / 0.0L;
  static long double minus_inf = -1.0L / 0.0L;
  memory_long_double m;

  /* A NaN can be recognized through its exponent.  But exclude +Infinity and
     -Infinity, which have the same exponent.  */
  m.value = x;
  if ((((m.word[LDBL_EXPBIT0_WORD] >> LDBL_EXPBIT0_BIT)
        ^ (nan.word[LDBL_EXPBIT0_WORD] >> LDBL_EXPBIT0_BIT))
       & LDBL_EXP_MASK)
      == 0)
    return (memcmp (&m.value, &plus_inf, sizeof (long double)) != 0
            && memcmp (&m.value, &minus_inf, sizeof (long double)) != 0);
  else
    return 0;
#else
  /* The configuration did not find sufficient information.  Give up about
     the signaling NaNs, handle only the quiet NaNs.  */
  if (x == x)
    return 0;
  else
    return 1;
#endif
}
================================ m4/isnanl.m4 =================================
# isnanl.m4 serial 1
dnl Copyright (C) 2007 Free Software Foundation, Inc.
dnl This file is free software; the Free Software Foundation
dnl gives unlimited permission to copy and/or distribute it,
dnl with or without modifications, as long as this notice is preserved.

AC_DEFUN([gl_FUNC_ISNANL_NO_LIBM],
[
  AC_REQUIRE([gt_TYPE_LONGDOUBLE])
  if test $gt_cv_c_long_double = yes; then
    AC_CHECK_FUNC([isnanl],
      [gl_cv_func_isnanl_no_libm=yes],
      [gl_cv_func_isnanl_no_libm=no])
    if test $gl_cv_func_isnanl_no_libm = yes; then
      AC_DEFINE([HAVE_ISNANL_IN_LIBC], 1,
        [Define if the isnanl() function is available in libc.])
    else
      AC_LIBOBJ([isnanl])
      gl_LONG_DOUBLE_EXPONENT_LOCATION
    fi
  fi
])

AC_DEFUN([gl_LONG_DOUBLE_EXPONENT_LOCATION],
[
  AC_CACHE_CHECK([where to find the exponent in a 'long double'],
    [gl_cv_cc_long_double_expbit0],
    [
      AC_TRY_RUN([
#include <float.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#define NWORDS \
  ((sizeof (long double) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
typedef union { long double value; unsigned int word[NWORDS]; }
        memory_long_double;
static unsigned int ored_words[NWORDS];
static unsigned int anded_words[NWORDS];
static void add_to_ored_words (long double x)
{
  memory_long_double m;
  size_t i;
  /* Clear it first, in case
     sizeof (long double) < sizeof (memory_long_double).  */
  memset (&m, 0, sizeof (memory_long_double));
  m.value = x;
  for (i = 0; i < NWORDS; i++)
    {
      ored_words[i] |= m.word[i];
      anded_words[i] &= m.word[i];
    }
}
int main ()
{
  size_t j;
  FILE *fp = fopen ("conftest.out", "w");
  if (fp == NULL)
    return 1;
  for (j = 0; j < NWORDS; j++)
    anded_words[j] = ~ (unsigned int) 0;
  add_to_ored_words (0.25L);
  add_to_ored_words (0.5L);
  add_to_ored_words (1.0L);
  add_to_ored_words (2.0L);
  add_to_ored_words (4.0L);
  /* Remove bits that are common (e.g. if representation of the first mantissa
     bit is explicit).  */
  for (j = 0; j < NWORDS; j++)
    ored_words[j] &= ~anded_words[j];
  /* Now find the nonzero word.  */
  for (j = 0; j < NWORDS; j++)
    if (ored_words[j] != 0)
      break;
  if (j < NWORDS)
    {
      size_t i;
      for (i = j + 1; i < NWORDS; i++)
        if (ored_words[i] != 0)
          {
            fprintf (fp, "unknown");
            return (fclose (fp) != 0);
          }
      for (i = 0; ; i++)
        if ((ored_words[j] >> i) & 1)
          {
            fprintf (fp, "word %d bit %d", (int) j, (int) i);
            return (fclose (fp) != 0);
          }
    }
  fprintf (fp, "unknown");
  return (fclose (fp) != 0);
}
        ],
        [gl_cv_cc_long_double_expbit0=`cat conftest.out`],
        [gl_cv_cc_long_double_expbit0="unknown"],
        [
          dnl When cross-compiling, we don't know. It depends on the
          dnl ABI and compiler version. There are too many cases.
          gl_cv_cc_long_double_expbit0="unknown"
        ])
      rm -f conftest.out
    ])
  case "$gl_cv_cc_long_double_expbit0" in
    word*bit*)
      word=`echo "$gl_cv_cc_long_double_expbit0" | sed -e 's/word //' -e 's/ 
bit.*//'`
      bit=`echo "$gl_cv_cc_long_double_expbit0" | sed -e 's/word.*bit //'`
      AC_DEFINE_UNQUOTED([LDBL_EXPBIT0_WORD], [$word],
        [Define as the word index where to find the exponent of 'long double'.])
      AC_DEFINE_UNQUOTED([LDBL_EXPBIT0_BIT], [$bit],
        [Define as the bit index in the word where to find bit 0 of the 
exponent of 'long double'.])
      ;;
  esac
])