# ldexpl.m4 serial 7
dnl Copyright (C) 2007-2010 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_LDEXPL],
[
  AC_REQUIRE([gl_MATH_H_DEFAULTS])
  dnl Check whether it's declared.
  dnl MacOS X 10.3 has ldexpl() in libc but doesn't declare it in <math.h>.
  AC_CHECK_DECL([ldexpl], , [HAVE_DECL_LDEXPL=0], [#include <math.h>])
  LDEXPL_LIBM=
  if test $HAVE_DECL_LDEXPL = 1; then
    gl_CHECK_LDEXPL_NO_LIBM
    if test $gl_cv_func_ldexpl_no_libm = no; then
      AC_CACHE_CHECK([whether ldexpl() can be used with libm],
        [gl_cv_func_ldexpl_in_libm],
        [
          save_LIBS="$LIBS"
          LIBS="$LIBS -lm"
          AC_TRY_LINK([#include <math.h>
                       long double x;],
                      [return ldexpl (x, -1) > 0;],
            [gl_cv_func_ldexpl_in_libm=yes],
            [gl_cv_func_ldexpl_in_libm=no])
          LIBS="$save_LIBS"
        ])
      if test $gl_cv_func_ldexpl_in_libm = yes; then
        LDEXPL_LIBM=-lm
      fi
    fi
    if test $gl_cv_func_ldexpl_no_libm = yes \
       || test $gl_cv_func_ldexpl_in_libm = yes; then
      save_LIBS="$LIBS"
      LIBS="$LIBS $LDEXPL_LIBM"
      gl_FUNC_LDEXPL_WORKS
      LIBS="$save_LIBS"
      case "$gl_cv_func_ldexpl_works" in
        *yes) gl_func_ldexpl=yes ;;
        *)    gl_func_ldexpl=no; REPLACE_LDEXPL=1; LDEXPL_LIBM= ;;
      esac
    else
      gl_func_ldexpl=no
    fi
    if test $gl_func_ldexpl = yes; then
      AC_DEFINE([HAVE_LDEXPL], [1],
        [Define if the ldexpl() function is available.])
    fi
  fi
  if test $HAVE_DECL_LDEXPL = 0 || test $gl_func_ldexpl = no; then
    AC_LIBOBJ([ldexpl])
  fi
  AC_SUBST([LDEXPL_LIBM])
])

dnl Test whether ldexpl() can be used without linking with libm.
dnl Set gl_cv_func_ldexpl_no_libm to 'yes' or 'no' accordingly.
AC_DEFUN([gl_CHECK_LDEXPL_NO_LIBM],
[
  AC_CACHE_CHECK([whether ldexpl() can be used without linking with libm],
    [gl_cv_func_ldexpl_no_libm],
    [
      AC_TRY_LINK([#include <math.h>
                   long double x;],
                  [return ldexpl (x, -1) > 0;],
        [gl_cv_func_ldexpl_no_libm=yes],
        [gl_cv_func_ldexpl_no_libm=no])
    ])
])

dnl Test whether ldexpl() works on finite numbers (this fails on AIX 5.1
dnl and MacOS X 10.4/PowerPC).
AC_DEFUN([gl_FUNC_LDEXPL_WORKS],
[
  AC_REQUIRE([AC_PROG_CC])
  AC_REQUIRE([AC_CANONICAL_HOST]) dnl for cross-compiles
  AC_CACHE_CHECK([whether ldexpl works], [gl_cv_func_ldexpl_works],
    [
      AC_TRY_RUN([
#include <math.h>
extern long double ldexpl (long double, int);
int main()
{
  volatile long double x1 = 1.0;
  volatile long double y1 = ldexpl (x1, -1);
  volatile long double x2 = 1.73205L;
  volatile long double y2 = ldexpl (x2, 0);
  return (y1 != 0.5L) || (y2 != x2);
}], [gl_cv_func_ldexpl_works=yes], [gl_cv_func_ldexpl_works=no],
      [
changequote(,)dnl
       case "$host_os" in
         aix | aix[3-6]*) gl_cv_func_ldexpl_works="guessing no";;
         *)               gl_cv_func_ldexpl_works="guessing yes";;
       esac
changequote([,])dnl
      ])
    ])
])