stringio.c: separate encoding from buffer

* ext/stringio/stringio.c (strio_set_encoding): add StringIO's own
  encoding and separate it from the buffer string to override the
  encoding of string when reading.  [ruby-core:72189] [Bug #11827]
  note that setting the encoding of its buffer string may cause
  unpredictable behavior.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@53188 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

1 files changed, 7 insertions, 0 deletions

diff --git a/test/stringio/test_stringio.rb b/test/stringio/test_stringio.rb
index 7b99d62f51..9a041c2148 100644
--- a/test/stringio/test_stringio.rb
+++ b/test/stringio/test_stringio.rb
@@ -148,6 +148,13 @@ class TestStringIO < Test::Unit::TestCase
       f.write(s)
     }
     assert_equal(Encoding::ASCII_8BIT, f.string.encoding, bug10285)
+
+    bug11827 = '[ruby-core:72189] [Bug #11827]'
+    f = StringIO.new("foo\x83".freeze)
+    assert_nothing_raised(RuntimeError, bug11827) {
+      f.set_encoding(Encoding::ASCII_8BIT)
+    }
+    assert_equal("foo\x83".b, f.gets)
   end
 
   def test_mode_error