diff --git a/ChangeLog b/ChangeLog
index 1dcf7a17b0..18651571b3 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,8 @@
+Wed Jan  7 17:13:38 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* instruby.rb (gem), lib/rubygems/defaults.rb (Gem.default_dir):
+	  use version invariant configuration.
+
 Tue Jan  6 19:09:51 2009  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* cont.c (cont_restore_0): streamlined to ensure O(1) time.  based on
diff --git a/common.mk b/common.mk
index 6550b1236c..2c673ee506 100644
--- a/common.mk
+++ b/common.mk
@@ -102,6 +102,7 @@ SCRIPT_ARGS   =	--dest-dir="$(DESTDIR)" \
 		--make-flags="$(MAKEFLAGS)"
 EXTMK_ARGS    =	$(SCRIPT_ARGS) --extension $(EXTS) --extstatic $(EXTSTATIC) \
 		--make-flags="MINIRUBY='$(MINIRUBY)'" --
+INSTRUBY      =	$(MINIRUBY) $(srcdir)/instruby.rb
 INSTRUBY_ARGS =	$(SCRIPT_ARGS) \
 		--data-mode=$(INSTALL_DATA_MODE) \
 		--prog-mode=$(INSTALL_PROG_MODE) \
@@ -166,72 +167,72 @@ install-all: install-nodoc install-doc install-capi
 install-nodoc: pre-install-nodoc do-install-nodoc post-install-nodoc
 pre-install-nodoc:: pre-install-local pre-install-ext
 do-install-nodoc: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --mantype="$(MANTYPE)"
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --mantype="$(MANTYPE)"
 post-install-nodoc:: post-install-local post-install-ext
 
 install-local: pre-install-local do-install-local post-install-local
 pre-install-local:: pre-install-bin pre-install-lib pre-install-man
 do-install-local: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=local --mantype="$(MANTYPE)"
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=local --mantype="$(MANTYPE)"
 post-install-local:: post-install-bin post-install-lib post-install-man
 
 install-ext: pre-install-ext do-install-ext post-install-ext
 pre-install-ext:: pre-install-ext-arch pre-install-ext-comm
 do-install-ext: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext
 post-install-ext:: post-install-ext-arch post-install-ext-comm
 
 install-arch: pre-install-arch do-install-arch post-install-arch
 pre-install-arch:: pre-install-bin pre-install-ext-arch
 do-install-arch: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin --install=ext-arch
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin --install=ext-arch
 post-install-arch:: post-install-bin post-install-ext-arch
 
 install-comm: pre-install-comm do-install-comm post-install-comm
 pre-install-comm:: pre-install-lib pre-install-ext-comm pre-install-man
 do-install-comm: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib --install=ext-comm --install=man
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib --install=ext-comm --install=man
 post-install-comm:: post-install-lib post-install-ext-comm post-install-man
 
 install-bin: pre-install-bin do-install-bin post-install-bin
 pre-install-bin:: install-prereq
 do-install-bin: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin
 post-install-bin::
 	@$(NULLCMD)
 
 install-lib: pre-install-lib do-install-lib post-install-lib
 pre-install-lib:: install-prereq
 do-install-lib: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib
 post-install-lib::
 	@$(NULLCMD)
 
 install-ext-comm: pre-install-ext-comm do-install-ext-comm post-install-ext-comm
 pre-install-ext-comm:: install-prereq
 do-install-ext-comm: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-comm
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-comm
 post-install-ext-comm::
 	@$(NULLCMD)
 
 install-ext-arch: pre-install-ext-arch do-install-ext-arch post-install-ext-arch
 pre-install-ext-arch:: install-prereq
 do-install-ext-arch: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-arch
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-arch
 post-install-ext-arch::
 	@$(NULLCMD)
 
 install-man: pre-install-man do-install-man post-install-man
 pre-install-man:: install-prereq
 do-install-man: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=man --mantype="$(MANTYPE)"
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=man --mantype="$(MANTYPE)"
 post-install-man::
 	@$(NULLCMD)
 
 install-capi: capi pre-install-capi do-install-capi post-install-capi
 pre-install-capi:: install-prereq
 do-install-capi: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=capi
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=capi
 post-install-capi::
 	@$(NULLCMD)
 
@@ -244,42 +245,42 @@ what-where-nodoc: no-install-nodoc
 no-install-nodoc: pre-no-install-nodoc dont-install-nodoc post-no-install-nodoc
 pre-no-install-nodoc:: pre-no-install-local pre-no-install-ext
 dont-install-nodoc:  $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --mantype="$(MANTYPE)"
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --mantype="$(MANTYPE)"
 post-no-install-nodoc:: post-no-install-local post-no-install-ext
 
 what-where-local: no-install-local
 no-install-local: pre-no-install-local dont-install-local post-no-install-local
 pre-no-install-local:: pre-no-install-bin pre-no-install-lib pre-no-install-man
 dont-install-local: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=local --mantype="$(MANTYPE)"
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=local --mantype="$(MANTYPE)"
 post-no-install-local:: post-no-install-bin post-no-install-lib post-no-install-man
 
 what-where-ext: no-install-ext
 no-install-ext: pre-no-install-ext dont-install-ext post-no-install-ext
 pre-no-install-ext:: pre-no-install-ext-arch pre-no-install-ext-comm
 dont-install-ext: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext
 post-no-install-ext:: post-no-install-ext-arch post-no-install-ext-comm
 
 what-where-arch: no-install-arch
 no-install-arch: pre-no-install-arch dont-install-arch post-no-install-arch
 pre-no-install-arch:: pre-no-install-bin pre-no-install-ext-arch
 dont-install-arch: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin --install=ext-arch
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin --install=ext-arch
 post-no-install-arch:: post-no-install-lib post-no-install-man post-no-install-ext-arch
 
 what-where-comm: no-install-comm
 no-install-comm: pre-no-install-comm dont-install-comm post-no-install-comm
 pre-no-install-comm:: pre-no-install-lib pre-no-install-ext-comm pre-no-install-man
 dont-install-comm: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib --install=ext-comm --install=man
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib --install=ext-comm --install=man
 post-no-install-comm:: post-no-install-lib post-no-install-ext-comm post-no-install-man
 
 what-where-bin: no-install-bin
 no-install-bin: pre-no-install-bin dont-install-bin post-no-install-bin
 pre-no-install-bin:: install-prereq
 dont-install-bin: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=bin
 post-no-install-bin::
 	@$(NULLCMD)
 
@@ -287,7 +288,7 @@ what-where-lib: no-install-lib
 no-install-lib: pre-no-install-lib dont-install-lib post-no-install-lib
 pre-no-install-lib:: install-prereq
 dont-install-lib: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=lib
 post-no-install-lib::
 	@$(NULLCMD)
 
@@ -295,7 +296,7 @@ what-where-ext-comm: no-install-ext-comm
 no-install-ext-comm: pre-no-install-ext-comm dont-install-ext-comm post-no-install-ext-comm
 pre-no-install-ext-comm:: install-prereq
 dont-install-ext-comm: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-comm
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-comm
 post-no-install-ext-comm::
 	@$(NULLCMD)
 
@@ -303,7 +304,7 @@ what-where-ext-arch: no-install-ext-arch
 no-install-ext-arch: pre-no-install-ext-arch dont-install-ext-arch post-no-install-ext-arch
 pre-no-install-ext-arch:: install-prereq
 dont-install-ext-arch: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-arch
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=ext-arch
 post-no-install-ext-arch::
 	@$(NULLCMD)
 
@@ -311,14 +312,14 @@ what-where-man: no-install-man
 no-install-man: pre-no-install-man dont-install-man post-no-install-man
 pre-no-install-man:: install-prereq
 dont-install-man: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=man --mantype="$(MANTYPE)"
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=man --mantype="$(MANTYPE)"
 post-no-install-man::
 	@$(NULLCMD)
 
 install-doc: rdoc pre-install-doc do-install-doc post-install-doc
 pre-install-doc:: install-prereq
 do-install-doc: $(PROGRAM)
-	$(MINIRUBY) $(srcdir)/instruby.rb --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc --rdoc-output="$(RDOCOUT)"
+	$(INSTRUBY) --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc --rdoc-output="$(RDOCOUT)"
 post-install-doc::
 	@$(NULLCMD)
 
@@ -330,7 +331,7 @@ what-where-doc: no-install-doc
 no-install-doc: pre-no-install-doc dont-install-doc post-no-install-doc
 pre-no-install-doc:: install-prereq
 dont-install-doc:: $(PREP)
-	$(MINIRUBY) $(srcdir)/instruby.rb -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc --rdoc-output="$(RDOCOUT)"
+	$(INSTRUBY) -n --make="$(MAKE)" $(INSTRUBY_ARGS) --install=rdoc --rdoc-output="$(RDOCOUT)"
 post-no-install-doc::
 	@$(NULLCMD)
 
diff --git a/instruby.rb b/instruby.rb
index ea9ef2a582..ff7de147cf 100755
--- a/instruby.rb
+++ b/instruby.rb
@@ -5,13 +5,14 @@ include RbConfig
 $".unshift File.expand_path("./rbconfig.rb")
 
 srcdir = File.dirname(__FILE__)
-$:.unshift File.expand_path("lib", srcdir)
+unless defined?(CROSS_COMPILING) and CROSS_COMPILING
+  $:.replace([File.expand_path("lib", srcdir), Dir.pwd])
+end
 require 'fileutils'
 require 'shellwords'
 require 'optparse'
 require 'optparse/shellwords'
 require 'tempfile'
-require 'rdoc/ri/paths'
 
 STDOUT.sync = true
 File.umask(0)
@@ -394,17 +395,13 @@ install?(:local, :comm, :man) do
     if $mantype == "doc"
       install mdoc, destfile, :mode => $data_mode
     else
-      require "../tool/mdoc2man.rb"
-
-      w = Tempfile.open(mdoc)
-
-      open(mdoc) { |r|
-        Mdoc2Man.mdoc2man(r, w)
-      }
-
-      w.close
+      require File.join(srcdir, "tool/mdoc2man.rb")
 
+      Tempfile.open(mdoc) do |w|
+        open(mdoc) {|r| Mdoc2Man.mdoc2man(r, w)}
+      end
       install w.path, destfile, :mode => $data_mode
+      w.close!
     end
   end
 end
@@ -412,7 +409,7 @@ end
 install?(:local, :comm, :gem) do
   puts "creating default gem directories"
 
-  gpath = Gem.default_dir
+  gpath = CONFIG["sitelibdir"].sub(%r'/site_ruby/(?=[^/]+)', '/gems/')
   makedirs Gem::DIRECTORIES.collect {|dir| File.join(gpath, dir)}
 end
 
diff --git a/lib/rubygems/defaults.rb b/lib/rubygems/defaults.rb
index 7884fad83d..995b81e1b2 100644
--- a/lib/rubygems/defaults.rb
+++ b/lib/rubygems/defaults.rb
@@ -20,12 +20,8 @@ module Gem
     if defined? RUBY_FRAMEWORK_VERSION then
       File.join File.dirname(ConfigMap[:sitedir]), 'Gems',
                 ConfigMap[:ruby_version]
-    elsif RUBY_VERSION > '1.9' then
-      File.join(ConfigMap[:libdir], ConfigMap[:ruby_install_name], 'gems',
-                ConfigMap[:ruby_version])
     else
-      File.join(ConfigMap[:libdir], ruby_engine, 'gems',
-                ConfigMap[:ruby_version])
+      ConfigMap[:sitelibdir].sub(%r'/site_ruby/(?=[^/]+)', '/gems/')
     end
   end