dnl EXTRA_COMPILE_WARNINGS
dnl Turn on many useful compiler warnings
dnl For now, only works on GCC
AC_DEFUN([EXTRA_COMPILE_WARNINGS],[
    dnl ******************************
    dnl More compiler warnings
    dnl ******************************

    AC_ARG_ENABLE(compile-warnings,
                  AC_HELP_STRING([--enable-compile-warnings=@<:@no/minimum/yes/maximum/error@:>@],
                                 [Turn on compiler warnings]),,
                  [enable_compile_warnings="m4_default([$1],[yes])"])

    warnCFLAGS=
    if test "x$GCC" != xyes; then
	enable_compile_warnings=no
    fi

    warning_flags=
    realsave_CFLAGS="$CFLAGS"

    case "$enable_compile_warnings" in
    no)
	warning_flags=
	;;
    minimum)
	warning_flags="-Wall"
	;;
    yes)
	warning_flags="-Wall -Wmissing-prototypes"
	;;
    maximum|error)
	warning_flags="-Wall -Wmissing-prototypes -Wnested-externs -Wpointer-arith"
	CFLAGS="$warning_flags $CFLAGS"
	for option in -Wno-sign-compare; do
		SAVE_CFLAGS="$CFLAGS"
		CFLAGS="$CFLAGS $option"
		AC_MSG_CHECKING([whether gcc understands $option])
		AC_TRY_COMPILE([], [],
			has_option=yes,
			has_option=no,)
		CFLAGS="$SAVE_CFLAGS"
		AC_MSG_RESULT($has_option)
		if test $has_option = yes; then
		  warning_flags="$warning_flags $option"
		fi
		unset has_option
		unset SAVE_CFLAGS
	done
	unset option
	if test "$enable_compile_warnings" = "error" ; then
	    warning_flags="$warning_flags -Werror"
	fi
	;;
    *)
	AC_MSG_ERROR(Unknown argument '$enable_compile_warnings' to --enable-compile-warnings)
	;;
    esac
    CFLAGS="$realsave_CFLAGS"
    AC_MSG_CHECKING(what warning flags to pass to the C compiler)
    AC_MSG_RESULT($warning_flags)

    AC_ARG_ENABLE(iso-c,
                  AC_HELP_STRING([--enable-iso-c],
                                 [Try to warn if code is not ISO C ]),,
                  [enable_iso_c=no])

    AC_MSG_CHECKING(what language compliance flags to pass to the C compiler)
    complCFLAGS=
    if test "x$enable_iso_c" != "xno"; then
	if test "x$GCC" = "xyes"; then
	case " $CFLAGS " in
	    *[\ \	]-ansi[\ \	]*) ;;
	    *) complCFLAGS="$complCFLAGS -ansi" ;;
	esac
	case " $CFLAGS " in
	    *[\ \	]-pedantic[\ \	]*) ;;
	    *) complCFLAGS="$complCFLAGS -pedantic" ;;
	esac
	fi
    fi
    AC_MSG_RESULT($complCFLAGS)

    WARN_CFLAGS="$warning_flags $complCFLAGS"
    AC_SUBST(WARN_CFLAGS)
])

dnl as-ac-expand.m4 0.2.0                                   -*- autoconf -*-
dnl autostars m4 macro for expanding directories using configure's prefix

dnl (C) 2003, 2004, 2005 Thomas Vander Stichele <thomas at apestaart dot org>

dnl Copying and distribution of this file, with or without modification,
dnl are permitted in any medium without royalty provided the copyright
dnl notice and this notice are preserved.

dnl AS_AC_EXPAND(VAR, CONFIGURE_VAR)

dnl example:
dnl AS_AC_EXPAND(SYSCONFDIR, $sysconfdir)
dnl will set SYSCONFDIR to /usr/local/etc if prefix=/usr/local

AC_DEFUN([AS_AC_EXPAND],
[
  EXP_VAR=[$1]
  FROM_VAR=[$2]

  dnl first expand prefix and exec_prefix if necessary
  prefix_save=$prefix
  exec_prefix_save=$exec_prefix

  dnl if no prefix given, then use /usr/local, the default prefix
  if test "x$prefix" = "xNONE"; then
    prefix="$ac_default_prefix"
  fi
  dnl if no exec_prefix given, then use prefix
  if test "x$exec_prefix" = "xNONE"; then
    exec_prefix=$prefix
  fi

  full_var="$FROM_VAR"
  dnl loop until it doesn't change anymore
  while true; do
    new_full_var="`eval echo $full_var`"
    if test "x$new_full_var" = "x$full_var"; then break; fi
    full_var=$new_full_var
  done

  dnl clean up
  full_var=$new_full_var
  AC_SUBST([$1], "$full_var")

  dnl restore prefix and exec_prefix
  prefix=$prefix_save
  exec_prefix=$exec_prefix_save
])