8000 bpo-44263: Py_TPFLAGS_HAVE_GC requires tp_traverse by vstinner · Pull Request #26463 · python/cpython · GitHub
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bpo-44263: Py_TPFLAGS_HAVE_GC requires tp_traverse #26463

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Merged
merged 1 commit into from
Jun 1, 2021
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bpo-44263: Py_TPFLAGS_HAVE_GC requires tp_traverse #26463

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7 changes: 6 additions & 1 deletion Doc/whatsnew/3.11.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -144,6 +144,11 @@ New Features
Porting to Python 3.11
----------------------

* The :c:func:`PyType_Ready` function now raises an error if a type is defined
with the :const:`Py_TPFLAGS_HAVE_GC` flag set but has no traverse function
(:c:member:`PyTypeObject.tp_traverse`).
(Contributed by Victor Stinner in :issue:`44263`.)

Deprecated
----------

Expand Down Expand Up @@ -180,4 +185,4 @@ Removed
parameter of functions :func:`~gettext.translation` and
:func:`~gettext.install` are also removed, since they are only used for
the ``l*gettext()`` functions.
(Contributed by Dong-hee Na and Serhiy Storchaka in :issue:`44235`.)
(Contributed by Dong-hee Na and Serhiy Storchaka in :issue:`44235`.)
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Why this change? :)

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Ask my text editor.

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My text editor (vim) likes to add newline at the end of a file.

4 changes: 4 additions & 0 deletions Misc/NEWS.d/next/C API/2021-05-31-11-31-13.bpo-44263.8mIOfV.rst
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@@ -0,0 +1,4 @@
The :c:func:`PyType_Ready` function now raises an error if a type is defined
with the :const:`Py_TPFLAGS_HAVE_GC` flag set but has no traverse function
(:c:member:`PyTypeObject.tp_traverse`).
Patch by Victor Stinner.
32 changes: 30 additions & 2 deletions Objects/typeobject.c
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Expand Up @@ -158,6 +158,12 @@ _PyType_CheckConsistency(PyTypeObject *type)
CHECK(!(type->tp_flags & Py_TPFLAGS_READYING));
CHECK(type->tp_dict != NULL);

if (type->tp_flags & Py_TPFLAGS_HAVE_GC) {
// bpo-44263: tp_traverse is required if Py_TPFLAGS_HAVE_GC is set.
// Note: tp_clear is optional.
CHECK(type->tp_traverse != NULL);
}

if (type->tp_flags & Py_TPFLAGS_DISALLOW_INSTANTIATION) {
CHECK(type->tp_new == NULL);
CHECK(_PyDict_ContainsId(type->tp_dict, &PyId___new__) == 0);
Expand Down Expand Up @@ -3607,6 +3613,7 @@ PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
}
}

assert(_PyType_CheckConsistency(type));
return (PyObject*)res;

fail:
Expand Down Expand Up @@ -5944,7 +5951,7 @@ static int add_tp_new_wrapper(PyTypeObject *type);
#define COLLECTION_FLAGS (Py_TPFLAGS_SEQUENCE | Py_TPFLAGS_MAPPING)

static int
type_ready_checks(PyTypeObject *type)
type_ready_pre_checks(PyTypeObject *type)
{
/* Consistency checks for PEP 590:
* - Py_TPFLAGS_METHOD_DESCRIPTOR requires tp_descr_get
Expand Down Expand Up @@ -6305,10 +6312,28 @@ type_ready_set_new(PyTypeObject *type)
}


static int
type_ready_post_checks(PyTypeObject *type)
{
// bpo-44263: tp_traverse is required if Py_TPFLAGS_HAVE_GC is set.
// Note: tp_clear is optional.
if (type->tp_flags & Py_TPFLAGS_HAVE_GC
&& type->tp_traverse == NULL)
{
PyErr_Format(PyExc_SystemError,
"type %s has the Py_TPFLAGS_HAVE_GC flag "
"but has no traverse function",
type->tp_name);
return -1;
}
return 0;
}


static int
type_ready(PyTypeObject *type)
{
if (type_ready_checks(type) < 0) {
if (type_ready_pre_checks(type) < 0) {
return -1;
}

Expand Down Expand Up @@ -6346,6 +6371,9 @@ type_ready(PyTypeObject *type)
if (type_ready_add_subclasses(type) < 0) {
return -1;
}
if (type_ready_post_checks(type) < 0) {
return -1;
}
return 0;
}

Expand Down
0