Milter-greylist

Sorry about all the inconvenience, see if this replacement definition
(place into configure.ac:94) would help you?

m4_define([__AC_UNDEFINE],[echo "#ifdef $1
  #undef $1
#endif" >>confdefs.h])


Or in "diff"/"patch" terms, this:

--- 
/home/jim/BuildNew/milter-greylist-buildzone/milter-greylist-cvs-jimbuild/configure.ac 
      2013-09-05 16:26:10.123813858 +0400
+++ configure.ac        2013-10-08 15:59:43.000000000 +0400
@@ -91,9 +91,9 @@
              _FIX_PACKAGE_URL=y
         fi])

-m4_define([__AC_UNDEFINE],[_AC_DEFINE_UNQUOTED([#ifdef $1
+m4_define([__AC_UNDEFINE],[echo "#ifdef $1
   #undef $1
-#endif])])
+#endif" >>confdefs.h])

  if test x"$_FIX_PACKAGE_NAME" = xy; then
      __AC_UNDEFINE([PACKAGE_NAME])

It seems to generate nearly the same shell code via autoconf.

If it works for you, there is a further cleanup patch on this
subject that I'd like to see tested on your system(s) please
(diff against tarball). This is basically the same, except that
it also adds a visible comment about redefinitions, and replaces
repeating double-lines (undef + def) with one routine (redef):

--- 
/home/jim/BuildNew/milter-greylist-buildzone/milter-greylist-cvs-jimbuild/configure.ac 
      2013-09-05 16:26:10.123813858 +0400
+++ configure.ac        2013-10-08 16:25:01.000000000 +0400
@@ -91,30 +91,31 @@
              _FIX_PACKAGE_URL=y
         fi])

-m4_define([__AC_UNDEFINE],[_AC_DEFINE_UNQUOTED([#ifdef $1
+m4_define([__AC_UNDEFINE],[echo "#ifdef $1
   #undef $1
-#endif])])
+#endif" >>confdefs.h])
+
+m4_define([__AC_REDEFINE],[echo \
+               "Redefining macro: '$1' into value '$2'; comment: '$3'"
+    __AC_UNDEFINE([$1])
+    AC_DEFINE_UNQUOTED([$1], [$2], [$3])
+])

  if test x"$_FIX_PACKAGE_NAME" = xy; then
-    __AC_UNDEFINE([PACKAGE_NAME])
-    AC_DEFINE_UNQUOTED([PACKAGE_NAME], ["$PACKAGE_NAME"], [Packaging 
metadata: distro source code name])
+    __AC_REDEFINE([PACKAGE_NAME], ["$PACKAGE_NAME"], [Packaging 
metadata: distro source code name])
  fi

  if test x"$_FIX_PACKAGE_VERSION" = xy; then
-    __AC_UNDEFINE([PACKAGE_VERSION])
-    AC_DEFINE_UNQUOTED([PACKAGE_VERSION], ["$PACKAGE_VERSION"], 
[Packaging metadata: distro source code version])
+    __AC_REDEFINE([PACKAGE_VERSION], ["$PACKAGE_VERSION"], [Packaging 
metadata: distro source code version])
  fi
  if test x"$_FIX_PACKAGE_STRING" = xy; then
-    __AC_UNDEFINE([PACKAGE_STRING])
-    AC_DEFINE_UNQUOTED([PACKAGE_STRING], ["$PACKAGE_STRING"], 
[Packaging metadata: distro source code name+version])
+    __AC_REDEFINE([PACKAGE_STRING], ["$PACKAGE_STRING"], [Packaging 
metadata: distro source code name+version])
  fi
  if test x"$_FIX_PACKAGE_URL" = xy; then
-    __AC_UNDEFINE([PACKAGE_URL])
-    AC_DEFINE_UNQUOTED([PACKAGE_URL], ["$PACKAGE_URL"], [Packaging 
metadata: distro contact])
+    __AC_REDEFINE([PACKAGE_URL], ["$PACKAGE_URL"], [Packaging metadata: 
distro contact])
  fi
  if test x"$_FIX_PACKAGE_BUGREPORT" = xy; then
-    __AC_UNDEFINE([PACKAGE_BUGREPORT])
-    AC_DEFINE_UNQUOTED([PACKAGE_BUGREPORT], ["$PACKAGE_BUGREPORT"], 
[Packaging metadata: distro contact])
+    __AC_REDEFINE([PACKAGE_BUGREPORT], ["$PACKAGE_BUGREPORT"], 
[Packaging metadata: distro contact])
  fi

  AC_DEFINE_UNQUOTED([PACKAGE_VERSION_UPSTREAM], 
["$PACKAGE_VERSION_UPSTREAM"], [Packaging metadata: upstream source code 
version])


   If this works for you, I'd like to submit the latter fix to Manu.

Thanks, and I hope this helps,
//Jim Klimov