diff --git a/config/ChangeLog b/config/ChangeLog
index 08b315d6e..5e417bdd2 100644
--- a/config/ChangeLog
+++ b/config/ChangeLog
@@ -1,3 +1,7 @@
+2004-09-24  Zack Weinberg  <zack@codesourcery.com>
+
+	* warnings.m4: New file.
+
 2004-09-23  H.J. Lu  <hongjiu.lu@intel.com>
 
 	PR bootstrap/17369
diff --git a/config/warnings.m4 b/config/warnings.m4
new file mode 100644
index 000000000..5501be920
--- /dev/null
+++ b/config/warnings.m4
@@ -0,0 +1,97 @@
+# Autoconf include file defining macros related to compile-time warnings.
+
+# Copyright 2004 Free Software Foundation, Inc.
+
+#This file is part of GCC.
+
+#GCC is free software; you can redistribute it and/or modify it under
+#the terms of the GNU General Public License as published by the Free
+#Software Foundation; either version 2, or (at your option) any later
+#version.
+
+#GCC is distributed in the hope that it will be useful, but WITHOUT
+#ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+#FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+#for more details.
+
+#You should have received a copy of the GNU General Public License
+#along with GCC; see the file COPYING.  If not, write to the Free
+#Software Foundation, 59 Temple Place - Suite 330, Boston, MA
+#02111-1307, USA.
+
+# ACX_PROG_CC_WARNING_OPTS([-Wfoo -Wbar -Wbaz])
+#   Sets @WARN_CFLAGS@ to the subset of the given options which the
+#   compiler accepts.
+AC_DEFUN([ACX_PROG_CC_WARNING_OPTS],
+[AC_REQUIRE([AC_PROG_CC])dnl
+AC_SUBST([WARN_CFLAGS])dnl
+WARN_CFLAGS=
+save_CFLAGS="$CFLAGS"
+for option in $1; do
+  AS_VAR_PUSHDEF([acx_Woption], [acx_cv_prog_cc_warning_$option])
+  AC_CACHE_CHECK([whether $CC supports $option], acx_Woption,
+    [CFLAGS="$option"
+    AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[])],
+      [AS_VAR_SET(acx_Woption, yes)],
+      [AS_VAR_SET(acx_Woption, no)])
+  ])
+  AS_IF([test AS_VAR_GET(acx_Woption) = yes],
+        [WARN_CFLAGS="$WARN_CFLAGS${WARN_CFLAGS:+ }$option"])
+  AS_VAR_POPDEF([acx_Woption])dnl
+done
+CFLAGS="$save_CFLAGS"
+])# ACX_PROG_CC_WARNING_OPTS
+
+# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC([-Wno-long-long ...])
+#   Sets WARN_PEDANTIC to "-pedantic" + the argument, if the compiler
+#   accepts all of those options simultaneously, otherwise to nothing.
+AC_DEFUN([ACX_PROG_CC_WARNING_ALMOST_PEDANTIC],
+[AC_REQUIRE([AC_PROG_CC])dnl
+AC_SUBST([WARN_PEDANTIC])dnl
+AS_VAR_PUSHDEF([acx_Pedantic], [acx_cv_prog_cc_pedantic_$1])dnl
+WARN_PEDANTIC=
+AC_CACHE_CHECK([whether $CC supports -pedantic $1], acx_Pedantic,
+[save_CFLAGS="$CFLAGS"
+CFLAGS="-pedantic $1"
+AC_COMPILE_IFELSE([AC_LANG_PROGRAM([],[])],
+   [AS_VAR_SET(acx_Pedantic, yes)],
+   [AS_VAR_SET(acx_Pedantic, no)])
+CFLAGS="$save_CFLAGS"])
+AS_IF([test AS_VAR_GET(acx_Pedantic) = yes],
+      [WARN_PEDANTIC="-pedantic $1"])
+AS_VAR_POPDEF([acx_Pedantic])dnl
+])# ACX_PROG_CC_WARNING_ALMOST_PEDANTIC
+
+# ACX_PROG_CC_WARNINGS_ARE_ERRORS([x.y.z])
+#   sets WERROR to "-Werror" if the compiler is GCC >=x.y.z, or if
+#   --enable-werror-always was given on the command line, otherwise
+#   to nothing.
+#   If the argument is the word "manual" instead of a version number,
+#   then WERROR will be set to -Werror only if --enable-werror-always
+#   appeared on the configure command line.
+AC_DEFUN([ACX_PROG_CC_WARNINGS_ARE_ERRORS],
+[AC_REQUIRE([AC_PROG_CC])dnl
+AC_SUBST([WERROR])dnl
+WERROR=
+AC_ARG_ENABLE(werror-always, 
+    AS_HELP_STRING([--enable-werror-always],
+		   [enable -Werror despite compiler version]),
+[], [enable_werror_always=no])
+AS_IF([test $enable_werror_always = yes],
+      [WERROR=-Werror],
+ m4_if($1, [manual],,
+ [AS_VAR_PUSHDEF([acx_GCCvers], [acx_cv_prog_cc_gcc_$1_or_newer])dnl
+  AC_CACHE_CHECK([whether $CC is GCC >=$1], acx_GCCvers,
+    [set fnord `echo $1 | tr '.' ' '`
+     shift
+     AC_PREPROC_IFELSE(
+[#if __GNUC__ * 10000 + __GNUC_MINOR__ * 100 + __GNUC_PATCHLEVEL__ \
+  < [$]1 * 10000 + [$]2 * 100 + [$]3
+#error insufficient
+#endif],
+   [AS_VAR_SET(acx_GCCvers, yes)],
+   [AS_VAR_SET(acx_GCCvers, no)])])
+ AS_IF([test AS_VAR_GET(acx_GCCvers) = yes],
+       [WERROR=-WerrorB])
+  AS_VAR_POPDEF([acx_GCCvers])]))
+])# ACX_PROG_CC_WARNINGS_ARE_ERRORS