# signbit.m4 serial 16
dnl Copyright (C) 2007-2018 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_SIGNBIT],
[
AC_REQUIRE([gl_MATH_H_DEFAULTS])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([for signbit macro], [gl_cv_func_signbit],
[
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[
#include <math.h>
/* If signbit is defined as a function, don't use it, since calling it for
'float' or 'long double' arguments would involve conversions.
If signbit is not declared at all but exists as a library function, don't
use it, since the prototype may not match.
If signbit is not declared at all but exists as a compiler built-in, don't
use it, since it's preferable to use __builtin_signbit* (no warnings,
no conversions). */
#ifndef signbit
# error "signbit should be a macro"
#endif
#include <string.h>
]gl_SIGNBIT_TEST_PROGRAM
])],
[gl_cv_func_signbit=yes],
[gl_cv_func_signbit=no],
[case "$host_os" in
# Guess yes on glibc systems.
*-gnu* | gnu*) gl_cv_func_signbit="guessing yes" ;;
# Guess yes on native Windows.
mingw*) gl_cv_func_signbit="guessing yes" ;;
# If we don't know, assume the worst.
*) gl_cv_func_signbit="guessing no" ;;
esac
])
])
dnl GCC 4.0 and newer provides three built-ins for signbit.
dnl They can be used without warnings, also in C++, regardless of <math.h>.
dnl But they may expand to calls to functions, which may or may not be in
dnl libc.
AC_CACHE_CHECK([for signbit compiler built-ins], [gl_cv_func_signbit_gcc],
[
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[
#if __GNUC__ >= 4
# define signbit(x) \
(sizeof (x) == sizeof (long double) ? __builtin_signbitl (x) : \
sizeof (x) == sizeof (double) ? __builtin_signbit (x) : \
__builtin_signbitf (x))
#else
# error "signbit should be three compiler built-ins"
#endif
#include <string.h>
]gl_SIGNBIT_TEST_PROGRAM
])],
[gl_cv_func_signbit_gcc=yes],
[gl_cv_func_signbit_gcc=no],
[case "$host_os" in
# Guess yes on glibc systems.
*-gnu* | gnu*) gl_cv_func_signbit_gcc="guessing yes" ;;
# Guess yes on mingw, no on MSVC.
mingw*) if test -n "$GCC"; then
gl_cv_func_signbit_gcc="guessing yes"
else
gl_cv_func_signbit_gcc="guessing no"
fi
;;
# If we don't know, assume the worst.
*) gl_cv_func_signbit_gcc="guessing no" ;;
esac
])
])
dnl Use the compiler built-ins whenever possible, because they are more
dnl efficient than the system library functions (if they exist).
case "$gl_cv_func_signbit_gcc" in
*yes)
REPLACE_SIGNBIT_USING_GCC=1
;;
*)
case "$gl_cv_func_signbit" in
*yes) ;;
*)
dnl REPLACE_SIGNBIT=1 makes sure the signbit[fdl] functions get built.
REPLACE_SIGNBIT=1
gl_FLOAT_SIGN_LOCATION
gl_DOUBLE_SIGN_LOCATION
gl_LONG_DOUBLE_SIGN_LOCATION
if test "$gl_cv_cc_float_signbit" = unknown; then
dnl Test whether copysignf() is declared.
AC_CHECK_DECLS([copysignf], , , [[#include <math.h>]])
if test "$ac_cv_have_decl_copysignf" = yes; then
dnl Test whether copysignf() can be used without libm.
AC_CACHE_CHECK([whether copysignf can be used without linking with libm],
[gl_cv_func_copysignf_no_libm],
[
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <math.h>
float x, y;]],
[[return copysignf (x, y) < 0;]])],
[gl_cv_func_copysignf_no_libm=yes],
[gl_cv_func_copysignf_no_libm=no])
])
if test $gl_cv_func_copysignf_no_libm = yes; then
AC_DEFINE([HAVE_COPYSIGNF_IN_LIBC], [1],
[Define if the copysignf function is declared in <math.h> and available in libc.])
fi
fi
fi
if test "$gl_cv_cc_double_signbit" = unknown; then
dnl Test whether copysign() is declared.
AC_CHECK_DECLS([copysign], , , [[#include <math.h>]])
if test "$ac_cv_have_decl_copysign" = yes; then
dnl Test whether copysign() can be used without libm.
AC_CACHE_CHECK([whether copysign can be used without linking with libm],
[gl_cv_func_copysign_no_libm],
[
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <math.h>
double x, y;]],
[[return copysign (x, y) < 0;]])],
[gl_cv_func_copysign_no_libm=yes],
[gl_cv_func_copysign_no_libm=no])
])
if test $gl_cv_func_copysign_no_libm = yes; then
AC_DEFINE([HAVE_COPYSIGN_IN_LIBC], [1],
[Define if the copysign function is declared in <math.h> and available in libc.])
fi
fi
fi
if test "$gl_cv_cc_long_double_signbit" = unknown; then
dnl Test whether copysignl() is declared.
AC_CHECK_DECLS([copysignl], , , [[#include <math.h>]])
if test "$ac_cv_have_decl_copysignl" = yes; then
dnl Test whether copysignl() can be used without libm.
AC_CACHE_CHECK([whether copysignl can be used without linking with libm],
[gl_cv_func_copysignl_no_libm],
[
AC_LINK_IFELSE(
[AC_LANG_PROGRAM(
[[#include <math.h>
long double x, y;]],
[[return copysignl (x, y) < 0;]])],
[gl_cv_func_copysignl_no_libm=yes],
[gl_cv_func_copysignl_no_libm=no])
])
if test $gl_cv_func_copysignl_no_libm = yes; then
AC_DEFINE([HAVE_COPYSIGNL_IN_LIBC], [1],
[Define if the copysignl function is declared in <math.h> and available in libc.])
fi
fi
fi
;;
esac
;;
esac
])
AC_DEFUN([gl_SIGNBIT_TEST_PROGRAM], [[
/* Global variables.
Needed because GCC 4 constant-folds __builtin_signbitl (literal)
but cannot constant-fold __builtin_signbitl (variable). */
float vf;
double vd;
long double vl;
int main ()
{
/* HP cc on HP-UX 10.20 has a bug with the constant expression -0.0.
So we use -p0f and -p0d instead. */
float p0f = 0.0f;
float m0f = -p0f;
double p0d = 0.0;
double m0d = -p0d;
/* On HP-UX 10.20, negating 0.0L does not yield -0.0L.
So we use another constant expression instead.
But that expression does not work on other platforms, such as when
cross-compiling to PowerPC on Mac OS X 10.5. */
long double p0l = 0.0L;
#if defined __hpux || defined __sgi
long double m0l = -LDBL_MIN * LDBL_MIN;
#else
long double m0l = -p0l;
#endif
int result = 0;
if (signbit (vf)) /* link check */
vf++;
{
float plus_inf = 1.0f / p0f;
float minus_inf = -1.0f / p0f;
if (!(!signbit (255.0f)
&& signbit (-255.0f)
&& !signbit (p0f)
&& (memcmp (&m0f, &p0f, sizeof (float)) == 0 || signbit (m0f))
&& !signbit (plus_inf)
&& signbit (minus_inf)))
result |= 1;
}
if (signbit (vd)) /* link check */
vd++;
{
double plus_inf = 1.0 / p0d;
double minus_inf = -1.0 / p0d;
if (!(!signbit (255.0)
&& signbit (-255.0)
&& !signbit (p0d)
&& (memcmp (&m0d, &p0d, sizeof (double)) == 0 || signbit (m0d))
&& !signbit (plus_inf)
&& signbit (minus_inf)))
result |= 2;
}
if (signbit (vl)) /* link check */
vl++;
{
long double plus_inf = 1.0L / p0l;
long double minus_inf = -1.0L / p0l;
if (signbit (255.0L))
result |= 4;
if (!signbit (-255.0L))
result |= 4;
if (signbit (p0l))
result |= 8;
if (!(memcmp (&m0l, &p0l, sizeof (long double)) == 0 || signbit (m0l)))
result |= 16;
if (signbit (plus_inf))
result |= 32;
if (!signbit (minus_inf))
result |= 64;
}
return result;
}
]])
AC_DEFUN([gl_FLOAT_SIGN_LOCATION],
[
gl_FLOATTYPE_SIGN_LOCATION([float], [gl_cv_cc_float_signbit], [f], [FLT])
])
AC_DEFUN([gl_DOUBLE_SIGN_LOCATION],
[
gl_FLOATTYPE_SIGN_LOCATION([double], [gl_cv_cc_double_signbit], [], [DBL])
])
AC_DEFUN([gl_LONG_DOUBLE_SIGN_LOCATION],
[
gl_FLOATTYPE_SIGN_LOCATION([long double], [gl_cv_cc_long_double_signbit], [L], [LDBL])
])
AC_DEFUN([gl_FLOATTYPE_SIGN_LOCATION],
[
AC_CACHE_CHECK([where to find the sign bit in a '$1'],
[$2],
[
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[
#include <stddef.h>
#include <stdio.h>
#define NWORDS \
((sizeof ($1) + sizeof (unsigned int) - 1) / sizeof (unsigned int))
typedef union { $1 value; unsigned int word[NWORDS]; }
memory_float;
static memory_float plus = { 1.0$3 };
static memory_float minus = { -1.0$3 };
int main ()
{
size_t j, k, i;
unsigned int m;
FILE *fp = fopen ("conftest.out", "w");
if (fp == NULL)
return 1;
/* Find the different bit. */
k = 0; m = 0;
for (j = 0; j < NWORDS; j++)
{
unsigned int x = plus.word[j] ^ minus.word[j];
if ((x & (x - 1)) || (x && m))
{
/* More than one bit difference. */
fprintf (fp, "unknown");
fclose (fp);
return 2;
}
if (x)
{
k = j;
m = x;
}
}
if (m == 0)
{
/* No difference. */
fprintf (fp, "unknown");
fclose (fp);
return 3;
}
/* Now m = plus.word[k] ^ ~minus.word[k]. */
if (plus.word[k] & ~minus.word[k])
{
/* Oh? The sign bit is set in the positive and cleared in the negative
numbers? */
fprintf (fp, "unknown");
fclose (fp);
return 4;
}
for (i = 0; ; i++)
if ((m >> i) & 1)
break;
fprintf (fp, "word %d bit %d", (int) k, (int) i);
if (fclose (fp) != 0)
return 5;
return 0;
}
]])],
[$2=`cat conftest.out`],
[$2="unknown"],
[
dnl When cross-compiling, we don't know. It depends on the
dnl ABI and compiler version. There are too many cases.
$2="unknown"
])
rm -f conftest.out
])
case "$]$2[" in
word*bit*)
word=`echo "$]$2[" | sed -e 's/word //' -e 's/ bit.*//'`
bit=`echo "$]$2[" | sed -e 's/word.*bit //'`
AC_DEFINE_UNQUOTED([$4][_SIGNBIT_WORD], [$word],
[Define as the word index where to find the sign of '$1'.])
AC_DEFINE_UNQUOTED([$4][_SIGNBIT_BIT], [$bit],
[Define as the bit index in the word where to find the sign of '$1'.])
;;
esac
])
# Expands to code that defines a function signbitf(float).
# It extracts the sign bit of a non-NaN value.
AC_DEFUN([gl_FLOAT_SIGNBIT_CODE],
[
gl_FLOATTYPE_SIGNBIT_CODE([float], [f], [f])
])
# Expands to code that defines a function signbitd(double).
# It extracts the sign bit of a non-NaN value.
AC_DEFUN([gl_DOUBLE_SIGNBIT_CODE],
[
gl_FLOATTYPE_SIGNBIT_CODE([double], [d], [])
])
# Expands to code that defines a function signbitl(long double).
# It extracts the sign bit of a non-NaN value.
AC_DEFUN([gl_LONG_DOUBLE_SIGNBIT_CODE],
[
gl_FLOATTYPE_SIGNBIT_CODE([long double], [l], [L])
])
AC_DEFUN([gl_FLOATTYPE_SIGNBIT_CODE],
[[
static int
signbit$2 ($1 value)
{
typedef union { $1 f; unsigned char b[sizeof ($1)]; } float_union;
static float_union plus_one = { 1.0$3 }; /* unused bits are zero here */
static float_union minus_one = { -1.0$3 }; /* unused bits are zero here */
/* Compute the sign bit mask as the XOR of plus_one and minus_one. */
float_union u;
unsigned int i;
u.f = value;
for (i = 0; i < sizeof ($1); i++)
if (u.b[i] & (plus_one.b[i] ^ minus_one.b[i]))
return 1;
return 0;
}
]])