Fix test_codecs for Windows: check size of wchar_t, not sys.maxunicode

Lib/test/test_codecs.py

@@ -3,6 +3,9 @@ import unittest
 import codecs
 import locale
 import sys, _testcapi, io
+import ctypes
+
+SIZEOF_WCHAR_T = ctypes.sizeof(ctypes.c_wchar)
 
 class Queue(object):
     """
@@ -888,10 +891,10 @@ class PunycodeTest(unittest.TestCase):
             self.assertEqual(uni, puny.decode("punycode"))
 
 class UnicodeInternalTest(unittest.TestCase):
+    @unittest.skipUnless(SIZEOF_WCHAR_T == 4, 'specific to 32-bit wchar_t')
     def test_bug1251300(self):
         # Decoding with unicode_internal used to not correctly handle "code
         # points" above 0x10ffff on UCS-4 builds.
-        if sys.maxunicode > 0xffff:
         ok = [
             (b"\x00\x10\xff\xff", "\U0010ffff"),
             (b"\x00\x00\x01\x01", "\U00000101"),
@@ -914,8 +917,8 @@ class UnicodeInternalTest(unittest.TestCase):
             self.assertRaises(UnicodeDecodeError, internal.decode,
                 "unicode_internal")
 
+    @unittest.skipUnless(SIZEOF_WCHAR_T == 4, 'specific to 32-bit wchar_t')
     def test_decode_error_attributes(self):
-        if sys.maxunicode > 0xffff:
         try:
             b"\x00\x00\x00\x00\x00\x11\x11\x00".decode("unicode_internal")
         except UnicodeDecodeError as ex:
@@ -926,8 +929,8 @@ class UnicodeInternalTest(unittest.TestCase):
         else:
             self.fail()
 
+    @unittest.skipUnless(SIZEOF_WCHAR_T == 4, 'specific to 32-bit wchar_t')
     def test_decode_callback(self):
-        if sys.maxunicode > 0xffff:
         codecs.register_error("UnicodeInternalTest", codecs.ignore_errors)
         decoder = codecs.getdecoder("unicode_internal")
         ab = "ab".encode("unicode_internal").decode()