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# frexp.m4 serial 2
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_FREXP],
[
AC_REQUIRE([gl_MATH_H_DEFAULTS])
FREXP_LIBM=
AC_CACHE_CHECK([whether frexp() can be used without linking with libm],
[gl_cv_func_frexp_no_libm],
[
AC_TRY_LINK([#include <math.h>
double x;],
[int e; return frexp (x, &e) > 0;],
[gl_cv_func_frexp_no_libm=yes],
[gl_cv_func_frexp_no_libm=no])
])
if test $gl_cv_func_frexp_no_libm = no; then
AC_CACHE_CHECK([whether frexp() can be used with libm],
[gl_cv_func_frexp_in_libm],
[
save_LIBS="$LIBS"
LIBS="$LIBS -lm"
AC_TRY_LINK([#include <math.h>
double x;],
[int e; return frexp (x, &e) > 0;],
[gl_cv_func_frexp_in_libm=yes],
[gl_cv_func_frexp_in_libm=no])
LIBS="$save_LIBS"
])
if test $gl_cv_func_frexp_in_libm = yes; then
FREXP_LIBM=-lm
fi
fi
if test $gl_cv_func_frexp_no_libm = yes \
|| test $gl_cv_func_frexp_in_libm = yes; then
save_LIBS="$LIBS"
LIBS="$LIBS $FREXP_LIBM"
gl_FUNC_FREXP_WORKS
LIBS="$save_LIBS"
case "$gl_cv_func_frexp_works" in
*yes) gl_func_frexp=yes ;;
*) gl_func_frexp=no; REPLACE_FREXP=1; FREXP_LIBM= ;;
esac
else
gl_func_frexp=no
fi
if test $gl_func_frexp = yes; then
AC_DEFINE([HAVE_FREXP], 1,
[Define if the frexp() function is available and works.])
else
AC_LIBOBJ([frexp])
fi
AC_SUBST([FREXP_LIBM])
])
dnl Test whether frexp() works also on denormalized numbers (this fails e.g. on
dnl NetBSD 3.0) and on infinite numbers (this fails e.g. on IRIX 6.5).
AC_DEFUN([gl_FUNC_FREXP_WORKS],
[
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([whether frexp works], [gl_cv_func_frexp_works],
[
AC_TRY_RUN([
#include <float.h>
#include <math.h>
int main()
{
int i;
volatile double x;
/* Test on denormalized numbers. */
for (i = 1, x = 1.0; i >= DBL_MIN_EXP; i--, x *= 0.5)
;
if (x > 0.0)
{
int exp;
double y = frexp (x, &exp);
/* On machines with IEEE754 arithmetic: x = 1.11254e-308, exp = -1022.
On NetBSD: y = 0.75. Correct: y = 0.5. */
if (y != 0.5)
return 1;
}
/* Test on infinite numbers. */
{
x = 1.0 / 0.0;
int exp;
double y = frexp (x, &exp);
if (y != x)
return 1;
}
return 0;
}], [gl_cv_func_frexp_works=yes], [gl_cv_func_frexp_works=no],
[case "$host_os" in
netbsd* | irix*) gl_cv_func_frexp_works="guessing no";;
*) gl_cv_func_frexp_works="guessing yes";;
esac
])
])
])
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