diff --git a/ChangeLog b/ChangeLog
index 841160149f..6497a832c5 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,11 @@
+Fri Dec 10 18:11:08 2010  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* lib/mkmf.rb (Logging.log_close): separate from Logging.logfile.
+
+	* test/mkmf/base.rb (TestMkmf::MKMFLOG): show mkmf.log at failures.
+
+	* test/mkmf/base.rb (TestMkmf#teardown): close log file for each tests.
+
 Fri Dec 10 11:36:43 2010  Kazuhiro NISHIYAMA  <zn@mbf.nifty.com>
 
 	* compile.c (enum): remove a comma at end of enumerator list.
diff --git a/lib/mkmf.rb b/lib/mkmf.rb
index 3e02886f67..d289cefca7 100644
--- a/lib/mkmf.rb
+++ b/lib/mkmf.rb
@@ -264,6 +264,10 @@ module Logging
 
   def self::logfile file
     @logfile = file
+    log_close
+  end
+
+  def self::log_close
     if @log and not @log.closed?
       @log.flush
       @log.close
diff --git a/test/mkmf/base.rb b/test/mkmf/base.rb
index 79f46ed202..4ceb35087a 100644
--- a/test/mkmf/base.rb
+++ b/test/mkmf/base.rb
@@ -9,6 +9,11 @@ $INCFLAGS << " -I."
 $extout_prefix = "$(extout)$(target_prefix)/"
 
 class TestMkmf < Test::Unit::TestCase
+  MKMFLOG = proc {File.read("mkmf.log") rescue ""}
+  class << MKMFLOG
+    alias to_s call
+  end
+
   def setup
     @tmpdir = Dir.mktmpdir
     @curdir = Dir.pwd
@@ -19,6 +24,7 @@ class TestMkmf < Test::Unit::TestCase
 
   def teardown
     Logging.quiet = @quiet
+    Logging.log_close
     Dir.chdir(@curdir)
     FileUtils.rm_rf(@tmpdir)
   end
diff --git a/test/mkmf/test_convertible.rb b/test/mkmf/test_convertible.rb
index 82189ff100..539998a3f4 100644
--- a/test/mkmf/test_convertible.rb
+++ b/test/mkmf/test_convertible.rb
@@ -6,7 +6,7 @@ class TestMkmf
       ["", ["signed ", ""], "unsigned "].each do |signed, prefix|
         %w[short int long].each do |type|
           assert_equal((prefix || signed)+type,
-                       mkmf {convertible_int(signed+type)})
+                       mkmf {convertible_int(signed+type)}, MKMFLOG)
         end
       end
     end
@@ -19,7 +19,7 @@ class TestMkmf
           }
           $defs.clear
           assert_equal((prefix || signed)+type,
-                       mkmf {convertible_int("test1_t", "confdefs.h")})
+                       mkmf {convertible_int("test1_t", "confdefs.h")}, MKMFLOG)
           (u = signed[/^u/]) and u.upcase!
           assert_includes($defs, "-DTYPEOF_TEST1_T="+"#{prefix||signed}#{type}".quote)
           assert_includes($defs, "-DPRI_TEST1T_PREFIX=PRI_#{type.upcase}_PREFIX")
diff --git a/test/mkmf/test_sizeof.rb b/test/mkmf/test_sizeof.rb
index a44e609c06..4e3c77e8e3 100644
--- a/test/mkmf/test_sizeof.rb
+++ b/test/mkmf/test_sizeof.rb
@@ -4,7 +4,7 @@ class TestMkmf
   class TestSizeof < TestMkmf
     def test_sizeof_builtin
       %w[char short int long float double void*].each do |type|
-        assert_kind_of(Integer, mkmf {check_sizeof(type)})
+        assert_kind_of(Integer, mkmf {check_sizeof(type)}, MKMFLOG)
       end
     end
 
@@ -12,7 +12,7 @@ class TestMkmf
       open("confdefs.h", "w") {|f|
         f.puts "typedef struct {char x;} test1_t;"
       }
-      assert_equal(1, mkmf {check_sizeof("test1_t", "confdefs.h")})
+      assert_equal(1, mkmf {check_sizeof("test1_t", "confdefs.h")}, MKMFLOG)
     end
   end
 end