stringio.c: use rb_str_append other than ASCII-8BIT

* ext/stringio/stringio.c (strio_write): use rb_str_append to
  reuse coderange bits other than ASCII-8BIT, and keep
  taintedness.  [ruby-dev:48118] [Bug #9769]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45677 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ChangeLog

@@ -1,3 +1,9 @@
+Wed Apr 23 11:03:41 2014  Nobuyoshi Nakada  <nobu@ruby-lang.org>
+
+	* ext/stringio/stringio.c (strio_write): use rb_str_append to
+	  reuse coderange bits other than ASCII-8BIT, and keep
+	  taintedness.  [ruby-dev:48118] [Bug #9769]
+
 Wed Apr 23 00:43:00 2014  NAKAMURA Usaku  <usa@ruby-lang.org>
 
 	* win32/win32.c, include/ruby/win32.h (ustatfs): implementation of

ext/stringio/stringio.c

@@ -1185,7 +1185,13 @@ strio_write(VALUE self, VALUE str)
 	ptr->pos = olen;
     }
     if (ptr->pos == olen) {
-	rb_enc_str_buf_cat(ptr->string, RSTRING_PTR(str), len, enc);
+	if (enc2 == rb_ascii8bit_encoding()) {
+	    rb_enc_str_buf_cat(ptr->string, RSTRING_PTR(str), len, enc);
+	    OBJ_INFECT(ptr->string, str);
+	}
+	else {
+	    rb_str_buf_append(ptr->string, str);
+	}
     }
     else {
 	strio_extend(ptr, ptr->pos, len);

test/stringio/test_stringio.rb

@@ -119,6 +119,24 @@ class TestStringIO < Test::Unit::TestCase
     f.close unless f.closed?
   end
 
+  def test_write_infection
+    bug9769 = '[ruby-dev:48118] [Bug #9769]'
+    s = "".untaint
+    f = StringIO.new(s, "w")
+    f.print("bar".taint)
+    f.close
+    assert_predicate(s, :tainted?, bug9769)
+  ensure
+    f.close unless f.closed?
+  end
+
+  def test_write_encoding
+    s = "".force_encoding(Encoding::UTF_8)
+    f = StringIO.new(s)
+    f.print("\u{3053 3093 306b 3061 306f ff01}".b)
+    assert_equal(Encoding::UTF_8, s.encoding, "honor the original encoding over ASCII-8BIT")
+  end
+
   def test_mode_error
     f = StringIO.new("", "r")
     assert_raise(IOError) { f.write("foo") }