Ensure result encoding is the same as input encoding for String#gsub. [Bug #4340].

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@30806 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,8 @@
+Sun Feb  6 12:46:02 2011  Eric Hodel  <drbrain@segment7.net>
+
+	* string.c (gsub): Ensure result encoding is the same as input
+	  encoding.  [Bug #4340].
+
 Sun Feb  6 12:18:25 2011  Nobuyoshi Nakada  <nobu@ruby-lang.org>
 
 	* parse.y (words, qwords): dispatch array events.  based on a

string.c

@@ -3745,6 +3745,7 @@ str_gsub(int argc, VALUE *argv, VALUE str, int bang)
     slen = RSTRING_LEN(str);
     cp = sp;
     str_enc = STR_ENC_GET(str);
+    rb_enc_associate(dest, str_enc);
 
     do {
 	n++;

test/ruby/test_string.rb

@@ -674,6 +674,21 @@ class TestString < Test::Unit::TestCase
     assert_raise(ArgumentError) { "foo".gsub }
   end
 
+  def test_gsub_encoding
+    a = S("hello world")
+    a.force_encoding Encoding::UTF_8
+
+    b = S("hi")
+    b.force_encoding Encoding::US_ASCII
+
+    assert_equal Encoding::UTF_8, a.gsub(/hello/, b).encoding
+
+    c = S("everybody")
+    c.force_encoding Encoding::US_ASCII
+
+    assert_equal Encoding::UTF_8, a.gsub(/world/, c).encoding
+  end
+
   def test_gsub!
     a = S("hello")
     b = a.dup