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 ******************************

    if test -z "$1" ; then
	default_compile_warnings=no
    else
	default_compile_warnings="$1"
    fi

    AC_ARG_ENABLE(compile-warnings, 
    [  --enable-compile-warnings=[no/minimum/yes/maximum/error]	Turn on compiler warnings.], [enable_compile_warnings="$default_compile_warnings"], enable_compile_warnings=yes)

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

    warning_flags=
    realsave_CFLAGS="$CFLAGS"

    case "$enable_compile_warnings" in
    no)
	warning_flags=
	;;
    minimum)
	warning_flags="-Wall -Wunused"
	;;
    yes)
	warning_flags="-Wall -Wunused -Wmissing-prototypes -Wmissing-declarations"
	;;
    maximum|error)
	warning_flags="-Wall -Wunused -Wchar-subscripts -Wmissing-declarations -Wmissing-prototypes -Wnested-externs -Wpointer-arith"
	CFLAGS="$warning_flags $CFLAGS"
	for option in -Wsign-promo -Wno-sign-compare; do
		SAVE_CFLAGS="$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,
    [  --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, 
    [  --enable-cxx-warnings=[no/minimum/yes]	Turn on compiler warnings.],,enable_cxx_warnings=minimum)

  AC_MSG_CHECKING(what warning flags to pass to the C++ compiler)
  warnCXXFLAGS=
  if test "x$GCC" != xyes; then
    enable_compile_warnings=no
  fi
  if test "x$enable_cxx_warnings" != "xno"; then
    if test "x$GCC" = "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 -Wmissing-prototypes -Wmissing-declarations -Wshadow -Woverloaded-virtual"
      fi
    fi
  fi
  AC_MSG_RESULT($warnCXXFLAGS)

   AC_ARG_ENABLE(iso-cxx,
     [  --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$enable_iso_cxx" != "xno"; then
     if test "x$GCC" = "xyes"; then
      case " $CXXFLAGS " in
      *[\ \	]-ansi[\ \	]*) ;;
      *) complCXXFLAGS="$complCXXFLAGS -ansi" ;;
      esac

      case " $CXXFLAGS " in
      *[\ \	]-pedantic[\ \	]*) ;;
      *) complCXXFLAGS="$complCXXFLAGS -pedantic" ;;
      esac
     fi
   fi
  AC_MSG_RESULT($complCXXFLAGS)
  if test "x$cxxflags_set" != "xyes"; then
    CXXFLAGS="$CXXFLAGS $warnCXXFLAGS $complCXXFLAGS"
    cxxflags_set=yes
    AC_SUBST(cxxflags_set)
  fi
])