8000 gh-93466: Document PyType_Spec doesn't accept repeated slot IDs; rais… · python/cpython@21a9a85 · GitHub
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gh-93466: Document PyType_Spec doesn't accept repeated slot IDs; raise where this was problematic (GH-93471)
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‎Doc/c-api/type.rst

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@@ -296,6 +296,8 @@ The following functions and structs are used to create
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Array of :c:type:`PyType_Slot` structures.
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Terminated by the special slot value ``{0, NULL}``.
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Each slot ID should be specified at most once.
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.. c:type:: PyType_Slot
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Structure defining optional functionality of a type, containing a slot ID

‎Lib/test/test_capi.py

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@@ -618,6 +618,12 @@ def test_heaptype_with_custom_metaclass(self):
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with self.assertRaisesRegex(TypeError, msg):
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t = _testcapi.pytype_fromspec_meta(_testcapi.HeapCTypeMetaclassCustomNew)
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def test_pytype_fromspec_with_repeated_slots(self):
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for variant in range(2):
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with self.subTest(variant=variant):
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with self.assertRaises(SystemError):
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_testcapi.create_type_from_repeated_slots(variant)
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621627
def test_pynumber_tobase(self):
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from _testcapi import pynumber_tobase
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self.assertEqual(pynumber_tobase(123, 2), '0b1111011')

‎Misc/NEWS.d/next/C API/2022-06-03-14-54-41.gh-issue-93466.DDtH0X.rst

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@@ -0,0 +1,3 @@
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Slot IDs in PyType_Spec may not be repeated. The documentation was updated
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to mention this. For some cases of repeated slots, PyType_FromSpec and
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related functions will now raise an exception.

‎Modules/_testcapimodule.c

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Original file line numberDiff line numberDiff line change
@@ -1482,6 +1482,63 @@ test_type_from_ephemeral_spec(PyObject *self, PyObject *Py_UNUSED(ignored))
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return result;
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}
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PyType_Slot repeated_doc_slots[] = {
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{Py_tp_doc, "A class used for tests·"},
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{Py_tp_doc, "A class used for tests"},
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{0, 0},
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};
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PyType_Spec repeated_doc_slots_spec = {
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.name = "RepeatedDocSlotClass",
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.basicsize = sizeof(PyObject),
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.slots = repeated_doc_slots,
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};
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typedef struct {
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PyObject_HEAD
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int data;
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} HeapCTypeWithDataObject;
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static struct PyMemberDef members_to_repeat[] = {
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{"T_INT", T_INT, offsetof(HeapCTypeWithDataObject, data), 0, NULL},
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{NULL}
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};
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PyType_Slot repeated_members_slots[] = {
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{Py_tp_members, members_to_repeat},
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{Py_tp_members, members_to_repeat},
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{0, 0},
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};
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PyType_Spec repeated_members_slots_spec = {
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.name = "RepeatedMembersSlotClass",
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.basicsize = sizeof(HeapCTypeWithDataObject),
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.slots = repeated_members_slots,
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};
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static PyObject *
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create_type_from_repeated_slots(PyObject *self, PyObject *variant_obj)
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{
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PyObject *class = NULL;
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int variant = PyLong_AsLong(variant_obj);
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if (PyErr_Occurred()) {
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return NULL;
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}
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switch (variant) {
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case 0:
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class = PyType_FromSpec(&repeated_doc_slots_spec);
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break;
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case 1:
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class = PyType_FromSpec(&repeated_members_slots_spec);
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break;
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default:
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PyErr_SetString(PyExc_ValueError, "bad test variant");
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break;
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}
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return class;
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}
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static PyObject *
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test_get_type_qualname(PyObject *self, PyObject *Py_UNUSED(ignored))
@@ -6107,6 +6164,8 @@ static PyMethodDef TestMethods[] = {
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{"test_get_type_name", test_get_type_name, METH_NOARGS},
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{"test_get_type_qualname", test_get_type_qualname, METH_NOARGS},
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{"test_type_from_ephemeral_spec", test_type_from_ephemeral_spec, METH_NOARGS},
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{"create_type_from_repeated_slots",
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create_type_from_repeated_slots, METH_O},
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{"test_from_spec_metatype_inheritance", test_from_spec_metatype_inheritance,
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METH_NOARGS},
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{"test_from_spec_invalid_metatype_inheritance",

‎Objects/typeobject.c

Lines changed: 14 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -3409,14 +3409,20 @@ PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module,
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int r;
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34113411
const PyType_Slot *slot;
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Py_ssize_t nmembers, weaklistoffset, dictoffset, vectorcalloffset;
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Py_ssize_t nmembers = 0;
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Py_ssize_t weaklistoffset, dictoffset, vectorcalloffset;
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char *res_start;
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short slot_offset, subslot_offset;
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34163417
nmembers = weaklistoffset = dictoffset = vectorcalloffset = 0;
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for (slot = spec->slots; slot->slot; slot++) {
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if (slot->slot == Py_tp_members) {
3419-
nmembers = 0;
3420+
if (nmembers != 0) {
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PyErr_SetString(
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PyExc_SystemError,
3423+
"Multiple Py_tp_members slots are not supported.");
3424+
return NULL;
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}
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for (const PyMemberDef *memb = slot->pfunc; memb->name != NULL; memb++) {
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nmembers++;
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if (strcmp(memb->name, "__weaklistoffset__") == 0) {
@@ -3559,6 +3565,12 @@ PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module,
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else if (slot->slot == Py_tp_doc) {
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/* For the docstring slot, which usually points to a static string
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literal, we need to make a copy */
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if (type->tp_doc != NULL) {
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PyErr_SetString(
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PyExc_SystemError,
3571+
"Multiple Py_tp_doc slots are not supported.");
3572+
return NULL;
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}
35623574
if (slot->pfunc == NULL) {
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type->tp_doc = NULL;
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continue;

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