diff --git a/test/gdbm/test_gdbm.rb b/test/gdbm/test_gdbm.rb
index 621101c9b3..38d97c1605 100644
--- a/test/gdbm/test_gdbm.rb
+++ b/test/gdbm/test_gdbm.rb
@@ -147,14 +147,14 @@ if defined? GDBM
     def test_s_open_lock
       return unless have_fork?	# snip this test
       pid = fork() {
-        assert_instance_of(GDBM, gdbm  = GDBM.open("#{@tmpdir}/#{@prefix}", 0644))
+        assert_instance_of(GDBM, GDBM.open("#{@tmpdir}/#{@prefix}", 0644))
         sleep 2
       }
       begin
         sleep 1
         assert_raise(Errno::EWOULDBLOCK) {
           begin
-            assert_instance_of(GDBM, gdbm2 = GDBM.open("#{@tmpdir}/#{@prefix}", 0644))
+            assert_instance_of(GDBM, GDBM.open("#{@tmpdir}/#{@prefix}", 0644))
           rescue Errno::EAGAIN, Errno::EACCES
             raise Errno::EWOULDBLOCK
           end
@@ -187,7 +187,7 @@ if defined? GDBM
       return unless have_fork?	# snip this test
 
       pid = fork() {
-        assert_instance_of(GDBM, gdbm  = GDBM.open("#{@tmpdir}/#{@prefix}", 0644,
+        assert_instance_of(GDBM, GDBM.open("#{@tmpdir}/#{@prefix}", 0644,
                                                   GDBM::NOLOCK))
         sleep 2
       }
@@ -202,10 +202,10 @@ if defined? GDBM
         gdbm2.close if gdbm2
       end
 
-      p Dir.glob("#{@tmpdir}/#{@prefix}*") if $DEBUG
+      STDERR.puts Dir.glob("#{@tmpdir}/#{@prefix}*") if $DEBUG
 
       pid = fork() {
-        assert_instance_of(GDBM, gdbm  = GDBM.open("#{@tmpdir}/#{@prefix}", 0644))
+        assert_instance_of(GDBM, GDBM.open("#{@tmpdir}/#{@prefix}", 0644))
         sleep 2
       }
       begin
diff --git a/test/ruby/test_econv.rb b/test/ruby/test_econv.rb
index 2f8ec49411..91c0792c33 100644
--- a/test/ruby/test_econv.rb
+++ b/test/ruby/test_econv.rb
@@ -44,9 +44,9 @@ class TestEncodingConverter < Test::Unit::TestCase
 
   def test_asciicompat_encoding_iso2022jp
     acenc = Encoding::Converter.asciicompat_encoding("ISO-2022-JP")
-    str = "\e$B~~\(B".force_encoding("iso-2022-jp")
+    str = "\e$B~~\e(B".force_encoding("iso-2022-jp")
     str2 = str.encode(acenc)
-    str3 = str.encode("ISO-2022-JP")
+    str3 = str2.encode("ISO-2022-JP")
     assert_equal(str, str3)
   end
 
@@ -147,7 +147,7 @@ class TestEncodingConverter < Test::Unit::TestCase
 
   def test_nil_source_buffer
     ec = Encoding::Converter.new("UTF-8", "EUC-JP")
-    ret = ec.primitive_convert(nil, dst="", nil, 10)
+    ret = ec.primitive_convert(nil, "", nil, 10)
     assert_equal(:finished, ret)
   end
 
@@ -475,44 +475,44 @@ class TestEncodingConverter < Test::Unit::TestCase
 
   def test_errinfo_invalid_euc_jp
     ec = Encoding::Converter.new("EUC-JP", "Shift_JIS")
-    ec.primitive_convert(src="\xff", dst="", nil, 10)
+    ec.primitive_convert("\xff", "", nil, 10)
     assert_errinfo(:invalid_byte_sequence, "EUC-JP", "Shift_JIS", "\xFF", "", ec)
   end
 
   def test_errinfo_invalid_euc_jp2
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert(src="\xff", dst="", nil, 10)
+    ec.primitive_convert("\xff", "", nil, 10)
     assert_errinfo(:invalid_byte_sequence, "EUC-JP", "UTF-8", "\xFF", "", ec)
   end
 
   def test_errinfo_undefined_hiragana
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert(src="\xa4\xa2", dst="", nil, 10)
+    ec.primitive_convert("\xa4\xa2", "", nil, 10)
     assert_errinfo(:undefined_conversion, "UTF-8", "ISO-8859-1", "\xE3\x81\x82", "", ec)
   end
 
   def test_errinfo_invalid_partial_character
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert(src="\xa4", dst="", nil, 10)
+    ec.primitive_convert("\xa4", "", nil, 10)
     assert_errinfo(:incomplete_input, "EUC-JP", "UTF-8", "\xA4", "", ec)
   end
 
   def test_errinfo_valid_partial_character
     ec = Encoding::Converter.new("EUC-JP", "ISO-8859-1")
-    ec.primitive_convert(src="\xa4", dst="", nil, 10, :partial_input=>true)
+    ec.primitive_convert("\xa4", "", nil, 10, :partial_input=>true)
     assert_errinfo(:source_buffer_empty, nil, nil, nil, nil, ec)
   end
 
   def test_errinfo_invalid_utf16be
     ec = Encoding::Converter.new("UTF-16BE", "UTF-8")
-    ec.primitive_convert(src="\xd8\x00\x00@", dst="", nil, 10)
+    ec.primitive_convert(src="\xd8\x00\x00@", "", nil, 10)
     assert_errinfo(:invalid_byte_sequence, "UTF-16BE", "UTF-8", "\xD8\x00", "\x00", ec)
     assert_equal("@", src)
   end
 
   def test_errinfo_invalid_utf16le
     ec = Encoding::Converter.new("UTF-16LE", "UTF-8")
-    ec.primitive_convert(src="\x00\xd8@\x00", dst="", nil, 10)
+    ec.primitive_convert(src="\x00\xd8@\x00", "", nil, 10)
     assert_errinfo(:invalid_byte_sequence, "UTF-16LE", "UTF-8", "\x00\xD8", "@\x00", ec)
     assert_equal("", src)
   end
@@ -599,7 +599,7 @@ class TestEncodingConverter < Test::Unit::TestCase
 
   def test_putback2
     ec = Encoding::Converter.new("utf-16le", "euc-jp")
-    ret = ec.primitive_convert(src="\x00\xd8\x21\x00", dst="", nil, nil)
+    ret = ec.primitive_convert("\x00\xd8\x21\x00", "", nil, nil)
     assert_equal(:invalid_byte_sequence, ret)
     assert_equal("\x00".force_encoding("utf-16le"), ec.putback(1))
     assert_equal("\x21".force_encoding("utf-16le"), ec.putback(1))
@@ -705,20 +705,20 @@ class TestEncodingConverter < Test::Unit::TestCase
   def test_last_error1
     ec = Encoding::Converter.new("sjis", "euc-jp")
     assert_equal(nil, ec.last_error)
-    assert_equal(:incomplete_input, ec.primitive_convert(src="fo\x81", dst="", nil, nil))
+    assert_equal(:incomplete_input, ec.primitive_convert("fo\x81", "", nil, nil))
     assert_kind_of(Encoding::InvalidByteSequenceError, ec.last_error)
   end
 
   def test_last_error2
     ec = Encoding::Converter.new("sjis", "euc-jp")
-    assert_equal("fo", ec.convert(src="fo\x81"))
+    assert_equal("fo", ec.convert("fo\x81"))
     assert_raise(Encoding::InvalidByteSequenceError) { ec.finish }
     assert_kind_of(Encoding::InvalidByteSequenceError, ec.last_error)
   end
 
   def test_us_ascii
     ec = Encoding::Converter.new("UTF-8", "US-ASCII")
-    ec.primitive_convert(src="\u{3042}", dst="")
+    ec.primitive_convert("\u{3042}", "")
     err = ec.last_error
     assert_kind_of(Encoding::UndefinedConversionError, err)
     assert_equal("\u{3042}", err.error_char)
@@ -726,7 +726,7 @@ class TestEncodingConverter < Test::Unit::TestCase
 
   def test_88591
     ec = Encoding::Converter.new("UTF-8", "ISO-8859-1")
-    ec.primitive_convert(src="\u{3042}", dst="")
+    ec.primitive_convert("\u{3042}", "")
     err = ec.last_error
     assert_kind_of(Encoding::UndefinedConversionError, err)
     assert_equal("\u{3042}", err.error_char)
diff --git a/test/test_securerandom.rb b/test/test_securerandom.rb
index be951ea722..f3e1bf0afc 100644
--- a/test/test_securerandom.rb
+++ b/test/test_securerandom.rb
@@ -87,7 +87,13 @@ end
           f << 'raise LoadError'
         }
         $LOAD_PATH.unshift(dir)
-        require 'securerandom'
+        v = $VERBOSE
+        begin
+          $VERBOSE = false
+          require 'securerandom'
+        ensure
+          $VERBOSE = v
+        end
         test_s_random_bytes
       end
     ensure
diff --git a/tool/compile_prelude.rb b/tool/compile_prelude.rb
index 1047e418b5..4f63b798c4 100755
--- a/tool/compile_prelude.rb
+++ b/tool/compile_prelude.rb
@@ -75,7 +75,7 @@ class Prelude
   end
 
   def emit(outfile)
-    init_name = outfile[/\w+(?=_prelude.c\b)/] || 'prelude'
+    @init_name = outfile[/\w+(?=_prelude.c\b)/] || 'prelude'
     erb = ERB.new(<<'EOS', nil, '%')
 /* -*-c-*-
  THIS FILE WAS AUTOGENERATED BY tool/compile_prelude.rb. DO NOT EDIT.
@@ -152,7 +152,7 @@ prelude_require(VALUE self, VALUE nth)
 
 % end
 void
-Init_<%=init_name%>(void)
+Init_<%=@init_name%>(void)
 {
 % if @have_sublib or @need_ruby_prefix
     struct prelude_env memo;
diff --git a/vm_exec.c b/vm_exec.c
index e72bc487df..6bd4f4e735 100644
--- a/vm_exec.c
+++ b/vm_exec.c
@@ -14,10 +14,10 @@
 #if VMDEBUG > 0
 #define DECL_SC_REG(type, r, reg) register type reg_##r
 
-#elif __GNUC__ && __x86_64__
+#elif defined(__GNUC__) && defined(_x86_64__)
 #define DECL_SC_REG(type, r, reg) register type reg_##r __asm__("r" reg)
 
-#elif __GNUC__ && __i386__
+#elif defined(__GNUC__) && defined(__i386__)
 #define DECL_SC_REG(type, r, reg) register type reg_##r __asm__("e" reg)
 
 #else
@@ -41,12 +41,12 @@ vm_exec_core(rb_thread_t *th, VALUE initial)
 #endif
 #endif
 
-#if __GNUC__ && __i386__
+#if defined(__GNUC__) && defined(__i386__)
     DECL_SC_REG(VALUE *, pc, "di");
     DECL_SC_REG(rb_control_frame_t *, cfp, "si");
 #define USE_MACHINE_REGS 1
 
-#elif __GNUC__ && __x86_64__
+#elif defined(__GNUC__) && defined(__x86_64__)
     DECL_SC_REG(VALUE *, pc, "14");
     DECL_SC_REG(rb_control_frame_t *, cfp, "15");
 #define USE_MACHINE_REGS 1
diff --git a/vm_exec.h b/vm_exec.h
index 4f8b030e68..2c1e2d5527 100644
--- a/vm_exec.h
+++ b/vm_exec.h
@@ -60,7 +60,7 @@ typedef rb_iseq_t *ISEQ;
 /* #define throwdebug printf */
 
 /************************************************/
-#if   DISPATCH_XXX
+#if defined(DISPATCH_XXX)
 error !
 /************************************************/
 #elif OPT_CALL_THREADED_CODE
@@ -95,7 +95,7 @@ error !
   INSN_ENTRY_SIG(insn); \
 
 /* dispather */
-#if __GNUC__ && (__i386__ || __x86_64__) && __GNUC__ == 3
+#if defined(__GNUC__) && (defined(__i386__) || defined(__x86_64__)) && __GNUC__ == 3
 #define DISPATCH_ARCH_DEPEND_WAY(addr) \
   asm volatile("jmp *%0;\t# -- inseted by vm.h\t[length = 2]" : : "r" (addr))