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-rw-r--r--Doc/c-api/type.rst26
-rw-r--r--Doc/whatsnew/3.12.rst20
-rw-r--r--Lib/test/test_capi/test_misc.py14
-rw-r--r--Misc/NEWS.d/next/C API/2023-04-28-18-04-38.gh-issue-103968.EnVvOx.rst4
-rw-r--r--Modules/_testcapi/heaptype.c16
-rw-r--r--Objects/typeobject.c38
6 files changed, 106 insertions, 12 deletions
diff --git a/Doc/c-api/type.rst b/Doc/c-api/type.rst
index 69b1529..9fd40e1 100644
--- a/Doc/c-api/type.rst
+++ b/Doc/c-api/type.rst
@@ -256,8 +256,13 @@ The following functions and structs are used to create
The metaclass *metaclass* is used to construct the resulting type object.
When *metaclass* is ``NULL``, the metaclass is derived from *bases*
(or *Py_tp_base[s]* slots if *bases* is ``NULL``, see below).
- Note that metaclasses that override
- :c:member:`~PyTypeObject.tp_new` are not supported.
+
+ Metaclasses that override :c:member:`~PyTypeObject.tp_new` are not
+ supported.
+ (For backwards compatibility, other ``PyType_From*`` functions allow
+ such metaclasses. They ignore ``tp_new``, which may result in incomplete
+ initialization. This is deprecated and in Python 3.14+ such metaclasses will
+ not be supported.)
The *bases* argument can be used to specify base classes; it can either
be only one class or a tuple of classes.
@@ -305,6 +310,11 @@ The following functions and structs are used to create
The function now finds and uses a metaclass corresponding to the provided
base classes. Previously, only :class:`type` instances were returned.
+ The :c:member:`~PyTypeObject.tp_new` of the metaclass is *ignored*.
+ which may result in incomplete initialization.
+ Creating classes whose metaclass overrides
+ :c:member:`~PyTypeObject.tp_new` is deprecated and in Python 3.14+ it
+ will be no longer allowed.
.. c:function:: PyObject* PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)
@@ -317,6 +327,12 @@ The following functions and structs are used to create
The function now finds and uses a metaclass corresponding to the provided
base classes. Previously, only :class:`type` instances were returned.
+ The :c:member:`~PyTypeObject.tp_new` of the metaclass is *ignored*.
+ which may result in incomplete initialization.
+ Creating classes whose metaclass overrides
+ :c:member:`~PyTypeObject.tp_new` is deprecated and in Python 3.14+ it
+ will be no longer allowed.
+
.. c:function:: PyObject* PyType_FromSpec(PyType_Spec *spec)
Equivalent to ``PyType_FromMetaclass(NULL, NULL, spec, NULL)``.
@@ -327,6 +343,12 @@ The following functions and structs are used to create
base classes provided in *Py_tp_base[s]* slots.
Previously, only :class:`type` instances were returned.
+ The :c:member:`~PyTypeObject.tp_new` of the metaclass is *ignored*.
+ which may result in incomplete initialization.
+ Creating classes whose metaclass overrides
+ :c:member:`~PyTypeObject.tp_new` is deprecated and in Python 3.14+ it
+ will be no longer allowed.
+
.. c:type:: PyType_Spec
Structure defining a type's behavior.
diff --git a/Doc/whatsnew/3.12.rst b/Doc/whatsnew/3.12.rst
index 3381ce7..63db5d3 100644
--- a/Doc/whatsnew/3.12.rst
+++ b/Doc/whatsnew/3.12.rst
@@ -1320,6 +1320,21 @@ Porting to Python 3.12
available on debug builds. If you happen to be using it then you'll
need to start using ``_Py_GetGlobalRefTotal()``.
+* The following functions now select an appropriate metaclass for the newly
+ created type:
+
+ * :c:func:`PyType_FromSpec`
+ * :c:func:`PyType_FromSpecWithBases`
+ * :c:func:`PyType_FromModuleAndSpec`
+
+ Creating classes whose metaclass overrides :c:member:`~PyTypeObject.tp_new`
+ is deprecated, and in Python 3.14+ it will be disallowed.
+ Note that these functions ignore ``tp_new`` of the metaclass, possibly
+ allowing incomplete initialization.
+
+ Note that :c:func:`PyType_FromMetaclass` (added in Python 3.12)
+ already disallows creating classes whose metaclass overrides ``tp_new``.
+
Deprecated
----------
@@ -1396,6 +1411,11 @@ Deprecated
* ``_PyErr_ChainExceptions`` is deprecated. Use ``_PyErr_ChainExceptions1``
instead. (Contributed by Irit Katriel in :gh:`102192`.)
+* Using :c:func:`PyType_FromSpec`, :c:func:`PyType_FromSpecWithBases`
+ or :c:func:`PyType_FromModuleAndSpec` to create a class whose metaclass
+ overrides :c:member:`~PyTypeObject.tp_new` is deprecated.
+ Call the metaclass instead.
+
Removed
-------
diff --git a/Lib/test/test_capi/test_misc.py b/Lib/test/test_capi/test_misc.py
index 9d5d1ca..1d426d0 100644
--- a/Lib/test/test_capi/test_misc.py
+++ b/Lib/test/test_capi/test_misc.py
@@ -681,6 +681,20 @@ class CAPITest(unittest.TestCase):
with self.assertRaisesRegex(TypeError, msg):
t = _testcapi.pytype_fromspec_meta(_testcapi.HeapCTypeMetaclassCustomNew)
+ def test_heaptype_with_custom_metaclass_deprecation(self):
+ # gh-103968: a metaclass with custom tp_new is deprecated, but still
+ # allowed for functions that existed in 3.11
+ # (PyType_FromSpecWithBases is used here).
+ class Base(metaclass=_testcapi.HeapCTypeMetaclassCustomNew):
+ pass
+
+ with warnings_helper.check_warnings(
+ ('.*custom tp_new.*in Python 3.14.*', DeprecationWarning),
+ ):
+ sub = _testcapi.make_type_with_base(Base)
+ self.assertTrue(issubclass(sub, Base))
+ self.assertIsInstance(sub, _testcapi.HeapCTypeMetaclassCustomNew)
+
def test_multiple_inheritance_ctypes_with_weakref_or_dict(self):
with self.assertRaises(TypeError):
diff --git a/Misc/NEWS.d/next/C API/2023-04-28-18-04-38.gh-issue-103968.EnVvOx.rst b/Misc/NEWS.d/next/C API/2023-04-28-18-04-38.gh-issue-103968.EnVvOx.rst
new file mode 100644
index 0000000..5e4270f
--- /dev/null
+++ b/Misc/NEWS.d/next/C API/2023-04-28-18-04-38.gh-issue-103968.EnVvOx.rst
@@ -0,0 +1,4 @@
+:c:func:`PyType_FromSpec` and its variants now allow creating classes whose
+metaclass overrides :c:member:`~PyTypeObject.tp_new`. The ``tp_new`` is
+ignored. This behavior is deprecated and will be disallowed in 3.14+. The
+new :c:func:`PyType_FromMetaclass` already disallows it.
diff --git a/Modules/_testcapi/heaptype.c b/Modules/_testcapi/heaptype.c
index 209cc18..6384fbc 100644
--- a/Modules/_testcapi/heaptype.c
+++ b/Modules/_testcapi/heaptype.c
@@ -22,7 +22,7 @@ static PyObject *pytype_fromspec_meta(PyObject* self, PyObject *meta)
"_testcapi.HeapCTypeViaMetaclass",
sizeof(PyObject),
0,
- Py_TPFLAGS_DEFAULT,
+ Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE,
HeapCTypeViaMetaclass_slots
};
@@ -385,6 +385,19 @@ make_immutable_type_with_base(PyObject *self, PyObject *base)
return PyType_FromSpecWithBases(&ImmutableSubclass_spec, base);
}
+static PyObject *
+make_type_with_base(PyObject *self, PyObject *base)
+{
+ assert(PyType_Check(base));
+ PyType_Spec ImmutableSubclass_spec = {
+ .name = "_testcapi.Subclass",
+ .basicsize = (int)((PyTypeObject*)base)->tp_basicsize,
+ .slots = empty_type_slots,
+ .flags = Py_TPFLAGS_DEFAULT,
+ };
+ return PyType_FromSpecWithBases(&ImmutableSubclass_spec, base);
+}
+
static PyMethodDef TestMethods[] = {
{"pytype_fromspec_meta", pytype_fromspec_meta, METH_O},
@@ -397,6 +410,7 @@ static PyMethodDef TestMethods[] = {
test_from_spec_invalid_metatype_inheritance,
METH_NOARGS},
{"make_immutable_type_with_base", make_immutable_type_with_base, METH_O},
+ {"make_type_with_base", make_type_with_base, METH_O},
{NULL},
};
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index cf0efe1..4ced04b 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -3950,9 +3950,10 @@ check_basicsize_includes_size_and_offsets(PyTypeObject* type)
return 1;
}
-PyObject *
-PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module,
- PyType_Spec *spec, PyObject *bases_in)
+static PyObject *
+_PyType_FromMetaclass_impl(
+ PyTypeObject *metaclass, PyObject *module,
+ PyType_Spec *spec, PyObject *bases_in, int _allow_tp_new)
{
/* Invariant: A non-NULL value in one of these means this function holds
* a strong reference or owns allocated memory.
@@ -4127,9 +4128,21 @@ PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module,
goto finally;
}
if (metaclass->tp_new != PyType_Type.tp_new) {
- PyErr_SetString(PyExc_TypeError,
- "Metaclasses with custom tp_new are not supported.");
- goto finally;
+ if (_allow_tp_new) {
+ if (PyErr_WarnFormat(
+ PyExc_DeprecationWarning, 1,
+ "Using PyType_Spec with metaclasses that have custom "
+ "tp_new is deprecated and will no longer be allowed in "
+ "Python 3.14.") < 0) {
+ goto finally;
+ }
+ }
+ else {
+ PyErr_SetString(
+ PyExc_TypeError,
+ "Metaclasses with custom tp_new are not supported.");
+ goto finally;
+ }
}
/* Calculate best base, and check that all bases are type objects */
@@ -4317,21 +4330,28 @@ PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module,
}
PyObject *
+PyType_FromMetaclass(PyTypeObject *metaclass, PyObject *module,
+ PyType_Spec *spec, PyObject *bases_in)
+{
+ return _PyType_FromMetaclass_impl(metaclass, module, spec, bases_in, 0);
+}
+
+PyObject *
PyType_FromModuleAndSpec(PyObject *module, PyType_Spec *spec, PyObject *bases)
{
- return PyType_FromMetaclass(NULL, module, spec, bases);
+ return _PyType_FromMetaclass_impl(NULL, module, spec, bases, 1);
}
PyObject *
PyType_FromSpecWithBases(PyType_Spec *spec, PyObject *bases)
{
- return PyType_FromMetaclass(NULL, NULL, spec, bases);
+ return _PyType_FromMetaclass_impl(NULL, NULL, spec, bases, 1);
}
PyObject *
PyType_FromSpec(PyType_Spec *spec)
{
- return PyType_FromMetaclass(NULL, NULL, spec, NULL);
+ return _PyType_FromMetaclass_impl(NULL, NULL, spec, NULL, 1);
}
PyObject *
generated by cgit v0.12 at 2025-01-23 17:32:02 (GMT)