Index: doc/autoconf.texi
===================================================================
RCS file: /sources/autoconf/autoconf/doc/autoconf.texi,v
retrieving revision 1.1119
diff -u -r1.1119 autoconf.texi
--- doc/autoconf.texi	15 Dec 2006 18:25:23 -0000	1.1119
+++ doc/autoconf.texi	16 Dec 2006 23:33:06 -0000
@@ -529,6 +529,7 @@
 * External Software::           Working with other optional software
 * Package Options::             Selecting optional features
 * Pretty Help Strings::         Formatting help string
+* Configure Option Checking::   Controlling checking of configure options
 * Site Details::                Configuring site details
 * Transforming Names::          Changing program names when installing
 * Site Defaults::               Giving @command{configure} local defaults
@@ -15445,6 +15446,7 @@
 * External Software::           Working with other optional software
 * Package Options::             Selecting optional features
 * Pretty Help Strings::         Formatting help string
+* Configure Option Checking::   Controlling checking of configure options
 * Site Details::                Configuring site details
 * Transforming Names::          Changing program names when installing
 * Site Defaults::               Giving @command{configure} local defaults
@@ -15515,14 +15517,15 @@
 @option{--without-@var{package}} is equivalent to
 @option{--with-@var{package}=no}.
 
-@command{configure} scripts do not complain about
-@option{--with-@var{package}} options that they do not support.  This
-behavior permits configuring a source tree containing multiple packages
-with a top-level @command{configure} script when the packages support
-different options, without spurious error messages about options that
-some of the packages support.  An unfortunate side effect is that option
-spelling errors are not diagnosed.  No better approach to this problem
-has been suggested so far.
+By default, @command{configure} scripts print a warning for
+@option{--with-@var{package}} options that they do not support.  They do
+not halt with an error in order to support configuring a source tree
+containing multiple packages with a top-level @command{configure} script
+when the packages support different options.  Furthermore, these
+warnings may be suppressed by the @option{--disable-option-checking}
+option or by calling @code{AC_DISABLE_OPTION_CHECKING} in
+@file{configure.ac}; this is the default if @code{AC_CONFIG_SUBDIRS} is
+called.
 
 For each external software package that may be used, @file{configure.ac}
 should call @code{AC_ARG_WITH} to detect whether the @command{configure}
@@ -15677,14 +15680,15 @@
 given, it defaults to @samp{yes}.  @option{--disable-@var{feature}} is
 equivalent to @option{--enable-@var{feature}=no}.
 
-@command{configure} scripts do not complain about
-@option{--enable-@var{feature}} options that they do not support.
-This behavior permits configuring a source tree containing multiple
-packages with a top-level @command{configure} script when the packages
-support different options, without spurious error messages about options
-that some of the packages support.
-An unfortunate side effect is that option spelling errors are not diagnosed.
-No better approach to this problem has been suggested so far.
+By default, @command{configure} scripts print a warning for
+@option{--enable-@var{feature}} options that they do not support.  They do
+not halt with an error in order to support configuring a source tree
+containing multiple packages with a top-level @command{configure} script
+when the packages support different options.  Furthermore, these
+warnings may be suppressed by the @option{--disable-option-checking}
+option or by calling @code{AC_DISABLE_OPTION_CHECKING} in
+@file{configure.ac}; this is the default if @code{AC_CONFIG_SUBDIRS} is
+called.
 
 For each optional feature, @file{configure.ac} should call
 @code{AC_ARG_ENABLE} to detect whether the @command{configure} user asked
@@ -15775,6 +15779,51 @@
 @end defmac
 
 
+@node Configure Option Checking
+@section Controlling Checking of Configure Options
+@cindex Options, Package
+
+The @command{configure} script checks the command-line options that are
+passed to it against a list of known options, like @option{--help} or
+@option{--config-cache}.  If an unknown option is passed, this
+ordinarily indicates a mistake by the user and @command{configure} halts
+with an error.  However, for unknown @option{--with-@var{package}} or
+@option{--enable-@var{feature}} options, by default only a warning
+message is printed (both at the beginning and end of the configure
+output).  The reason for this behavior and how it may be modified are
+as follows.
+
+It not uncommon to configure a source tree containing multiple packages
+with a top-level @command{configure} script, via the
+@code{AC_CONFIG_SUBDIRS} macro.  Because the packages generally support
+different @option{--with-@var{package}} and
+@option{--enable-@var{feature}} options, however, they must accept
+unrecognized options without halting.  (For the same reason, this
+behavior is required by the GNU Coding Standards.)  In such cases, even
+a warning message is undesirable, and so @code{AC_CONFIG_SUBDIRS}
+automatically disables the warnings.
+
+This behavior may be modified in two other ways.  First, the user can
+pass @option{--disable-option-checking} to @command{configure} in order
+to disable the warnings, or conversely
+@option{--enable-option-checking=fatal} makes @command{configure} halt
+with an error for unrecognized options.  Second, the @file{configure.ac}
+file may call @code{AC_DISABLE_OPTION_CHECKING}:
+
+@defmac AC_DISABLE_OPTION_CHECKING
+@acindex{DISABLE_OPTION_CHECKING}
+
+By default, disable warnings for unrecognized
+@option{--with-@var{package}} or @option{--enable-@var{feature}}
+options.  This is implied by @code{AC_CONFIG_SUBDIRS}.
+
+The user may still override this behavior by passing
+@option{--enable-option-checking} (enable warnings) or
+@option{--enable-option-checking=fatal} (enable errors) to
+@command{configure}.
+@end defmac
+
+
 @node Site Details
 @section Configuring Site Details
 @cindex Site details
Index: lib/autoconf/general.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/autoconf/general.m4,v
retrieving revision 1.943
diff -u -r1.943 general.m4
--- lib/autoconf/general.m4	15 Dec 2006 18:25:23 -0000	1.943
+++ lib/autoconf/general.m4	16 Dec 2006 23:33:06 -0000
@@ -409,6 +409,7 @@
 m4_wrap([m4_divert_text([DEFAULTS],
 [ac_subst_vars='m4_ifdef([_AC_SUBST_VARS],  [m4_defn([_AC_SUBST_VARS])])'
 ac_subst_files='m4_ifdef([_AC_SUBST_FILES], [m4_defn([_AC_SUBST_FILES])])'
+ac_user_opts=':enable_option_checking:m4_ifdef([_AC_USER_OPTS], [m4_defn([_AC_USER_OPTS])]):'
 m4_ifdef([_AC_PRECIOUS_VARS],
   [_AC_ARG_VAR_STORE[]dnl
    _AC_ARG_VAR_VALIDATE[]dnl
@@ -878,6 +879,15 @@
   AC_MSG_ERROR([missing argument to $ac_option])
 fi
 
+if test "x$ac_unrecognized_opts" != x; then
+   ac_unrecognized_opts=`echo $ac_unrecognized_opts | sed 's/^, //'`
+   case $enable_option_checking in
+     no) ac_unrecognized_opts="" ;;
+     fatal) AC_MSG_ERROR([Unrecognized options: $ac_unrecognized_opts]) ;;
+     *)      AC_MSG_WARN([Unrecognized options: $ac_unrecognized_opts]) ;;
+   esac
+fi
+
 # Be sure to have absolute directory names.
 for ac_var in	exec_prefix prefix bindir sbindir libexecdir datarootdir \
 		datadir sysconfdir sharedstatedir localstatedir includedir \
@@ -947,6 +957,10 @@
       AC_MSG_ERROR(
 	[invalid ]m4_if([$2], [with], [package], [feature])[ name: $ac_useropt])
     ac_useropt=`AS_ECHO(["$ac_useropt"]) | sed 's/[[-.]]/_/g'`
+    case $ac_user_opts in
+      *:$2_$ac_useropt:*) ;;
+      *) ac_unrecognized_opts="$ac_unrecognized_opts, --$1-$ac_useropt" ;;
+    esac
     eval $2_$ac_useropt=m4_if([$1], [$2], [\$ac_optarg], [no]) ;;dnl
 ])
 
@@ -985,6 +999,7 @@
   -C, --config-cache      alias for \`--cache-file=config.cache'
   -n, --no-create         do not create output files
       --srcdir=DIR        find the sources in DIR [configure dir or \`..']
+  --disable-option-checking    ignore unrecognized --enable/--with options
 
 Installation directories:
   --prefix=PREFIX         install architecture-independent files in PREFIX
@@ -1373,7 +1388,8 @@
 ])
 
 m4_define([_AC_ENABLE_IF_ACTION],
-[AS_IF([test "${$1_$2+set}" = set], [$1val=$$1_$2; $3], [$4])dnl
+[m4_append_uniq([_AC_USER_OPTS], [$1_$2], [:])dnl
+AS_IF([test "${$1_$2+set}" = set], [$1val=$$1_$2; $3], [$4])dnl
 ])
 
 # AC_ARG_ENABLE(FEATURE, HELP-STRING, [ACTION-IF-TRUE], [ACTION-IF-FALSE])
@@ -1410,6 +1426,11 @@
 AU_DEFUN([AC_WITH],
 [AC_ARG_WITH([$1], [  --with-$1], [$2], [$3])])
 
+# AC_DISABLE_OPTION_CHECKING
+# --------------------------------------------------------------------
+AC_DEFUN([AC_DISABLE_OPTION_CHECKING],
+[m4_divert_once([DEFAULTS], [enable_option_checking=no])
+])# AC_DISABLE_OPTION_CHECKING
 
 
 ## ----------------------------------------- ##
Index: lib/autoconf/status.m4
===================================================================
RCS file: /sources/autoconf/autoconf/lib/autoconf/status.m4,v
retrieving revision 1.124
diff -u -r1.124 status.m4
--- lib/autoconf/status.m4	7 Dec 2006 05:16:59 -0000	1.124
+++ lib/autoconf/status.m4	16 Dec 2006 23:33:06 -0000
@@ -987,6 +987,7 @@
 #   This is used in _AC_OUTPUT_SUBDIRS.
 AC_DEFUN([AC_CONFIG_SUBDIRS],
 [AC_REQUIRE([AC_CONFIG_AUX_DIR_DEFAULT])dnl
+AC_REQUIRE([AC_DISABLE_OPTION_CHECKING])dnl
 m4_foreach_w([_AC_Sub], [$1],
 	     [_AC_CONFIG_UNIQUE([SUBDIRS],
 				m4_bpatsubst(m4_defn([_AC_Sub]), [:.*]))])dnl
@@ -1009,7 +1010,8 @@
 #
 if test "$no_recursion" != yes; then
 
-  # Remove --cache-file and --srcdir arguments so they do not pile up.
+  # Remove --cache-file, --srcdir, and --disable-option-checking arguments
+  # so they do not pile up.
   ac_sub_configure_args=
   ac_prev=
   eval "set x $ac_configure_args"
@@ -1038,6 +1040,8 @@
       ac_prev=prefix ;;
     -prefix=* | --prefix=* | --prefi=* | --pref=* | --pre=* | --pr=* | --p=*)
       ;;
+    --disable-option-checking)
+      ;;
     *)
       case $ac_arg in
       *\'*) ac_arg=`AS_ECHO(["$ac_arg"]) | sed "s/'/'\\\\\\\\''/g"` ;;
@@ -1059,6 +1063,10 @@
     ac_sub_configure_args="--silent $ac_sub_configure_args"
   fi
 
+  # Always prepend --disable-option-checking to silence warnings, since
+  # different subdirs can have different --enable and --with options.
+  ac_sub_configure_args="--disable-option-checking $ac_sub_configure_args"
+
   ac_popdir=`pwd`
   for ac_dir in : $subdirs; do test "x$ac_dir" = x: && continue
 
@@ -1186,6 +1194,9 @@
 fi
 dnl config.status should not do recursion.
 AC_PROVIDE_IFELSE([AC_CONFIG_SUBDIRS], [_AC_OUTPUT_SUBDIRS()])dnl
+if test "x$ac_unrecognized_opts" != x; then
+   AC_MSG_WARN([Unrecognized options: $ac_unrecognized_opts])
+fi
 ])# AC_OUTPUT