diff --git a/ChangeLog b/ChangeLog
index d7e020d5bb..8315a5d879 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+Thu Nov 18 07:37:44 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* Makefile.in (reconfig): force reconfigure with previous options.
+
+	* common.mk (showconfig): show configure flags, like as
+	  `config.status --config' generated by recent autoconf.
+
 Thu Nov 18 07:16:49 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* missing/langinfo.c (strncasecmp): get rid of redefinition.
diff --git a/Makefile.in b/Makefile.in
index ce4d71d0b1..076e96e63a 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -145,6 +145,8 @@ SRC_FILE      = $<
 
 MESSAGE_BEGIN = @for line in
 MESSAGE_END = ; do echo "$$line"; done
+
+configure_args = @configure_args@
 #### End of variables
 
 all:
@@ -223,10 +225,15 @@ $(MKFILES): config.status
 uncommon.mk: $(srcdir)/common.mk
 		sed 's/{\$$([^(){}]*)[^{}]*}//g' $< > $@
 
-config.status:	$(srcdir)/configure $(srcdir)/enc/Makefile.in
+.PHONY: reconfig
+reconfig-args = $(srcdir)/configure $(configure_args)
+config.status-args = ./config.status --recheck
+reconfig-exec-0 = exec 3>&1; exit `exec 4>&1; { "$$@" 3>&- 4>&-; echo $$? 1>&4; } | fgrep -v '(cached)' 1>&3`
+reconfig-exec-1 = set -x; "$$@"
+
+reconfig config.status:	$(srcdir)/configure $(srcdir)/enc/Makefile.in
 	@PWD= MINIRUBY="$(MINIRUBY)"; export MINIRUBY; \
-	set $(SHELL) ./config.status --recheck; \
-	exec 3>&1; exit `exec 4>&1; { "$$@" 3>&- 4>&-; echo $$? 1>&4; } | fgrep -v '(cached)' 1>&3`
+	set $(SHELL) $($@-args); $(reconfig-exec-$(V))
 
 $(srcdir)/configure: $(srcdir)/configure.in
 	$(CHDIR) $(srcdir) && exec $(AUTOCONF)
diff --git a/common.mk b/common.mk
index 9846c55ee4..8d4d0de744 100644
--- a/common.mk
+++ b/common.mk
@@ -150,6 +150,12 @@ showflags:
 	"	SOLIBS = $(SOLIBS)" \
 	$(MESSAGE_END)
 
+.PHONY: showconfig
+showconfig:
+	@$(MESSAGE_BEGIN) \
+	"$(configure_args)" \
+	$(MESSAGE_END)
+
 exts: $(MKMAIN_CMD)
 
 $(MKMAIN_CMD): $(MKFILES) incs $(PREP) $(RBCONFIG) $(LIBRUBY)