bpo-29240: PEP 540: Add a new UTF-8 Mode (#855)

* Add -X utf8 command line option, PYTHONUTF8 environment variable
  and a new sys.flags.utf8_mode flag.
* If the LC_CTYPE locale is "C" at startup: enable automatically the
  UTF-8 mode.
* Add _winapi.GetACP(). encodings._alias_mbcs() now calls
  _winapi.GetACP() to get the ANSI code page
* locale.getpreferredencoding() now returns 'UTF-8' in the UTF-8
  mode. As a side effect, open() now uses the UTF-8 encoding by
  default in this mode.
* Py_DecodeLocale() and Py_EncodeLocale() now use the UTF-8 encoding
  in the UTF-8 Mode.
* Update subprocess._args_from_interpreter_flags() to handle -X utf8
* Skip some tests relying on the current locale if the UTF-8 mode is
  enabled.
* Add test_utf8mode.py.
* _Py_DecodeUTF8_surrogateescape() gets a new optional parameter to
  return also the length (number of wide characters).
* pymain_get_global_config() and pymain_set_global_config() now
  always copy flag values, rather than only copying if the new value
  is greater than the old value.

1 files changed, 4 insertions, 2 deletions

diff --git a/Python/sysmodule.c b/Python/sysmodule.c
index f10099b523..141e189d0b 100644
--- a/Python/sysmodule.c
+++ b/Python/sysmodule.c
@@ -1814,6 +1814,7 @@ static PyStructSequence_Field flags_fields[] = {
     {"hash_randomization",      "-R"},
     {"isolated",                "-I"},
     {"dev_mode",                "-X dev"},
+    {"utf8_mode",               "-X utf8"},
     {0}
 };
 
@@ -1821,7 +1822,7 @@ static PyStructSequence_Desc flags_desc = {
     "sys.flags",        /* name */
     flags__doc__,       /* doc */
     flags_fields,       /* fields */
-    14
+    15
 };
 
 static PyObject*
@@ -1853,8 +1854,9 @@ make_flags(void)
     SetFlag(Py_QuietFlag);
     SetFlag(Py_HashRandomizationFlag);
     SetFlag(Py_IsolatedFlag);
-#undef SetFlag
     PyStructSequence_SET_ITEM(seq, pos++, PyBool_FromLong(core_config->dev_mode));
+    SetFlag(Py_UTF8Mode);
+#undef SetFlag
 
     if (PyErr_Occurred()) {
         Py_DECREF(seq);