bpo-43916: Add Py_TPFLAGS_DISALLOW_INSTANTIATION type flag (GH-25721)
Add a new Py_TPFLAGS_DISALLOW_INSTANTIATION type flag to disallow
creating type instances: set tp_new to NULL and don't create the
"__new__" key in the type dictionary.
The flag is set automatically on static types if tp_base is NULL or
&PyBaseObject_Type and tp_new is NULL.
Use the flag on the following types:
* _curses.ncurses_version type
* _curses_panel.panel
* _tkinter.Tcl_Obj
* _tkinter.tkapp
* _tkinter.tktimertoken
* _xxsubinterpretersmodule.ChannelID
* sys.flags type
* sys.getwindowsversion() type
* sys.version_info type
Update MyStr example in the C API documentation to use
Py_TPFLAGS_DISALLOW_INSTANTIATION.
Add _PyStructSequence_InitType() function to create a structseq type
with the Py_TPFLAGS_DISALLOW_INSTANTIATION flag set.
type_new() calls _PyType_CheckConsistency() at exit.
diff --git a/Modules/_cursesmodule.c b/Modules/_cursesmodule.c
index d221cf1..bcf9ad1 100644
--- a/Modules/_cursesmodule.c
+++ b/Modules/_cursesmodule.c
@@ -4793,9 +4793,11 @@ PyInit__curses(void)
#ifdef NCURSES_VERSION
/* ncurses_version */
if (NcursesVersionType.tp_name == NULL) {
- if (PyStructSequence_InitType2(&NcursesVersionType,
- &ncurses_version_desc) < 0)
+ if (_PyStructSequence_InitType(&NcursesVersionType,
+ &ncurses_version_desc,
+ Py_TPFLAGS_DISALLOW_INSTANTIATION) < 0) {
return NULL;
+ }
}
v = make_ncurses_version();
if (v == NULL) {
@@ -4803,15 +4805,6 @@ PyInit__curses(void)
}
PyDict_SetItemString(d, "ncurses_version", v);
Py_DECREF(v);
-
- /* prevent user from creating new instances */
- NcursesVersionType.tp_init = NULL;
- NcursesVersionType.tp_new = NULL;
- if (PyDict_DelItemString(NcursesVersionType.tp_dict, "__new__") < 0 &&
- PyErr_ExceptionMatches(PyExc_KeyError))
- {
- PyErr_Clear();
- }
#endif /* NCURSES_VERSION */
SetDictInt("ERR", ERR);