Use _Py_STR for "utf-8"

Author: methane

Modules/_io/textio.c

@@ -1145,10 +1145,10 @@ _io_TextIOWrapper___init___impl(textio *self, PyObject *buffer,
         }
     }
     if (encoding == NULL && self->encoding == NULL) {
-        const PyPreConfig *preconfig = &_PyRuntime.preconfig;
-        if (preconfig->utf8_mode) {
-            // TODO: Use _Py_STR
-            self->encoding = PyUnicode_FromString("utf-8");
+        if (_PyRuntime.preconfig.utf8_mode) {
+            _Py_DECLARE_STR(utf_8, "utf-8");
+            self->encoding = &_Py_STR(utf_8);
+            Py_INCREF(self->encoding);
         }
         else {
             self->encoding = _Py_GetLocaleEncodingObject();

Python/fileutils.c

@@ -94,7 +94,10 @@ _Py_device_encoding(int fd)
     return PyUnicode_FromFormat("cp%u", (unsigned int)cp);
 #else
     if (_PyRuntime.preconfig.utf8_mode) {
-        return PyUnicode_FromString("utf-8"); //TODO: Use _Py_STR
+        _Py_DECLARE_STR(utf_8, "utf-8");
+        PyObject *encoding = &_Py_STR(utf_8);
+        Py_INCREF(encoding);
+        return encoding;
     }
     return _Py_GetLocaleEncodingObject();
 #endif