dnl AS_AC_EXPAND(VAR, CONFIGURE_VAR)

dnl

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

])

dnl GNOME_COMPILE_WARNINGS

dnl Turn on many useful compiler warnings

dnl For now, only works on GCC

AC_DEFUN([GNOME_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 For C++, do basically the same thing.

AC_DEFUN([GNOME_CXX_WARNINGS],[

  AC_ARG_ENABLE(cxx-warnings,

                AC_HELP_STRING([--enable-cxx-warnings=@<:@no/minimum/yes@:>@]

                               [Turn on compiler warnings.]),,

                [enable_cxx_warnings="m4_default([$1],[minimum])"])

  AC_MSG_CHECKING(what warning flags to pass to the C++ compiler)

  warnCXXFLAGS=

  if test "x$GXX" != xyes; then

    enable_cxx_warnings=no

  fi

  if test "x$enable_cxx_warnings" != "xno"; then

    if test "x$GXX" = "xyes"; then

      case " $CXXFLAGS " in

      *[\ \	]-Wall[\ \	]*) ;;

      *) warnCXXFLAGS="-Wall -Wno-unused" ;;

      esac

      ## -W is not all that useful.  And it cannot be controlled

      ## with individual -Wno-xxx flags, unlike -Wall

      if test "x$enable_cxx_warnings" = "xyes"; then

	warnCXXFLAGS="$warnCXXFLAGS -Wshadow -Woverloaded-virtual"

      fi

    fi

  fi

  AC_MSG_RESULT($warnCXXFLAGS)

   AC_ARG_ENABLE(iso-cxx,

                 AC_HELP_STRING([--enable-iso-cxx],

                                [Try to warn if code is not ISO C++ ]),,

                 [enable_iso_cxx=no])

   AC_MSG_CHECKING(what language compliance flags to pass to the C++ compiler)

   complCXXFLAGS=

   if test "x$enable_iso_cxx" != "xno"; then

     if test "x$GXX" = "xyes"; then

      case " $CXXFLAGS " in

      *[\ \	]-ansi[\ \	]*) ;;

      *) complCXXFLAGS="$complCXXFLAGS -ansi" ;;

      esac

      case " $CXXFLAGS " in

      *[\ \	]-pedantic[\ \	]*) ;;

      *) complCXXFLAGS="$complCXXFLAGS -pedantic" ;;

      esac

     fi

   fi

  AC_MSG_RESULT($complCXXFLAGS)

  WARN_CXXFLAGS="$CXXFLAGS $warnCXXFLAGS $complCXXFLAGS"

  AC_SUBST(WARN_CXXFLAGS)

])