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bpo-43916: Add Py_TPFLAGS_DISALLOW_INSTANTIATION type flag (GH-25721)

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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.
This commit is contained in:
Victor Stinner 2021-04-30 12:46:15 +02:00 • committed by GitHub
parent b73b5fb9ea
commit 3bb09947ec
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GPG key ID: 4AEE18F83AFDEB23
13 changed files with 144 additions and 102 deletions
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12
Objects/structseq.c
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@ -459,8 +459,10 @@ initialize_members(PyStructSequence_Desc *desc, PyMemberDef* members,
members[k].name = NULL;
}
int
PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
_PyStructSequence_InitType(PyTypeObject *type, PyStructSequence_Desc *desc,
unsigned long tp_flags)
{
PyMemberDef *members;
Py_ssize_t n_members, n_unnamed_members;
@ -488,7 +490,7 @@ PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
type->tp_base = &PyTuple_Type;
type->tp_methods = structseq_methods;
type->tp_new = structseq_new;
type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC;
type->tp_flags = Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC | tp_flags;
type->tp_traverse = (traverseproc) structseq_traverse;
n_members = count_members(desc, &n_unnamed_members);
@ -516,6 +518,12 @@ PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
return 0;
}
int
PyStructSequence_InitType2(PyTypeObject *type, PyStructSequence_Desc *desc)
{
return _PyStructSequence_InitType(type, desc, 0);
}
void
PyStructSequence_InitType(PyTypeObject *type, PyStructSequence_Desc *desc)
{