Merge 3.5

Lib/test/multibytecodec_support.py

@@ -270,6 +270,13 @@ class TestBase:
 
                 self.assertEqual(ostream.getvalue(), self.tstring[0])
 
+    def test_streamwriter_reset_no_pending(self):
+        # Issue #23247: Calling reset() on a fresh StreamWriter instance
+        # (without pending data) must not crash
+        stream = BytesIO()
+        writer = self.writer(stream)
+        writer.reset()
+
 
 class TestBase_Mapping(unittest.TestCase):
     pass_enctest = []

Misc/NEWS

@@ -185,6 +185,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #23247: Fix a crash in the StreamWriter.reset() of CJK codecs.
+
 - Issue #24270: Add math.isclose() and cmath.isclose() functions as per PEP 485.
   Contributed by Chris Barker and Tal Einat.
 

Modules/cjkcodecs/multibytecodec.c

@@ -1685,6 +1685,9 @@ _multibytecodec_MultibyteStreamWriter_reset_impl(MultibyteStreamWriterObject *se
 {
     PyObject *pwrt;
 
+    if (!self->pending)
+        Py_RETURN_NONE;
+
     pwrt = multibytecodec_encode(self->codec, &self->state,
                     self->pending, NULL, self->errors,
                     MBENC_FLUSH | MBENC_RESET);