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# ldexp.m4 serial 2
dnl Copyright (C) 2010-2023 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_LDEXP],
[
AC_REQUIRE([gl_MATH_H_DEFAULTS])
AC_REQUIRE([gl_FUNC_ISNAND]) dnl for ISNAND_LIBM
AC_REQUIRE([gl_CHECK_LDEXP_NO_LIBM])
LDEXP_LIBM=
if test $gl_cv_func_ldexp_no_libm = no; then
AC_CACHE_CHECK([whether ldexp() can be used with libm],
[gl_cv_func_ldexp_in_libm],
[
save_LIBS="$LIBS"
LIBS="$LIBS -lm"
AC_LINK_IFELSE(
[AC_LANG_PROGRAM([[#ifndef __NO_MATH_INLINES
# define __NO_MATH_INLINES 1 /* for glibc */
#endif
#include <math.h>
double (*funcptr) (double, int) = ldexp;
double x;]],
[[return ldexp (x, -1) > 0;]])],
[gl_cv_func_ldexp_in_libm=yes],
[gl_cv_func_ldexp_in_libm=no])
LIBS="$save_LIBS"
])
if test $gl_cv_func_ldexp_in_libm = yes; then
LDEXP_LIBM=-lm
fi
fi
save_LIBS="$LIBS"
LIBS="$LIBS $LDEXP_LIBM"
gl_FUNC_LDEXP_WORKS
LIBS="$save_LIBS"
case "$gl_cv_func_ldexp_works" in
*yes) ;;
*) REPLACE_LDEXP=1 ;;
esac
if test $REPLACE_LDEXP = 1; then
dnl Find libraries needed to link lib/ldexp.c.
LDEXP_LIBM="$ISNAND_LIBM"
fi
AC_SUBST([LDEXP_LIBM])
])
dnl Test whether ldexp() can be used without linking with libm.
dnl Set gl_cv_func_ldexp_no_libm to 'yes' or 'no' accordingly.
AC_DEFUN([gl_CHECK_LDEXP_NO_LIBM],
[
AC_CACHE_CHECK([whether ldexp() can be used without linking with libm],
[gl_cv_func_ldexp_no_libm],
[
AC_LINK_IFELSE(
[AC_LANG_PROGRAM([[#ifndef __NO_MATH_INLINES
# define __NO_MATH_INLINES 1 /* for glibc */
#endif
#include <math.h>
double (*funcptr) (double, int) = ldexp;
double x;]],
[[return ldexp (x, -1) > 0;]])],
[gl_cv_func_ldexp_no_libm=yes],
[gl_cv_func_ldexp_no_libm=no])
])
])
dnl Test whether ldexp() works (this fails on OpenBSD 7.3/mips64).
AC_DEFUN([gl_FUNC_LDEXP_WORKS],
[
AC_REQUIRE([AC_PROG_CC])
AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
AC_CACHE_CHECK([whether ldexp works], [gl_cv_func_ldexp_works],
[
AC_RUN_IFELSE(
[AC_LANG_SOURCE([[
#include <math.h>
int main()
{
int result = 0;
{
volatile double x = 1.9269695883136991774e-308;
volatile double y = ldexp (x, 0);
if (y != x)
result |= 1;
}
return result;
}]])],
[gl_cv_func_ldexp_works=yes],
[gl_cv_func_ldexp_works=no],
[case "$host_os" in
openbsd*) gl_cv_func_ldexp_works="guessing no" ;;
# Guess yes on native Windows.
mingw* | windows*) gl_cv_func_ldexp_works="guessing yes" ;;
*) gl_cv_func_ldexp_works="guessing yes" ;;
esac
])
])
])
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