* string.c (tr_trans): when the hash for multibyte repl is empty,

tr is inverse mode, and a character doesn't much the table, the
  character should be replaced by last replacement. Bug #4449

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30977 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Mon Feb 28 16:28:15 2011  NARUSE, Yui  <naruse@ruby-lang.org>
+
+	* string.c (tr_trans): when the hash for multibyte repl is empty,
+	  tr is inverse mode, and a character doesn't much the table, the
+	  character should be replaced by last replacement. Bug #4449
+
 Mon Feb 28 16:38:56 2011  Tanaka Akira  <akr@fsij.org>
 
 	* ext/openssl/ossl_ocsp.c: parenthesize macro arguments.

string.c

@@ -5060,7 +5060,7 @@ tr_trans(VALUE str, VALUE src, VALUE repl, int sflag)
 		else c = NUM2INT(tmp);
 	    }
 	    else {
-		c = errc;
+		c = cflag ? last : errc;
 	    }
 	    if (c != errc) {
 		tlen = rb_enc_codelen(c, enc);

test/ruby/test_m17n.rb

@@ -962,6 +962,7 @@ class TestM17N < Test::Unit::TestCase
 
     assert_equal("X\u3042\u3044X", "A\u3042\u3044\u3046".tr("^\u3042\u3044", "X"))
     assert_equal("\u3042\u3046" * 100, ("\u3042\u3044" * 100).tr("\u3044", "\u3046"))
+    assert_equal("Y", "\u3042".tr("^X", "Y"))
   end
 
   def test_tr_s