From a452fce1f51fecee449c5f43c5563884aa3d2187 Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Wed, 19 Nov 2025 19:11:37 +0200 Subject: [PATCH 1/2] gh-41779: Allow defining any __slots__ for a class derived from tuple --- Doc/reference/datamodel.rst | 3 ++- Doc/whatsnew/3.15.rst | 4 ++++ Include/descrobject.h | 1 + Lib/test/test_descr.py | 15 +++++++++++++ ...5-11-19-20-42-21.gh-issue-41779.Psz9Vo.rst | 3 +++ Objects/typeobject.c | 15 ++++++++++--- Python/specialize.c | 9 ++++++++ Python/structmember.c | 21 +++++++++++++------ 8 files changed, 61 insertions(+), 10 deletions(-) create mode 100644 Misc/NEWS.d/next/Core_and_Builtins/2025-11-19-20-42-21.gh-issue-41779.Psz9Vo.rst diff --git a/Doc/reference/datamodel.rst b/Doc/reference/datamodel.rst index ebadbc215a0eed..356953fd24e74e 100644 --- a/Doc/reference/datamodel.rst +++ b/Doc/reference/datamodel.rst @@ -2633,7 +2633,7 @@ Notes on using *__slots__*: * :exc:`TypeError` will be raised if *__slots__* other than *__dict__* and *__weakref__* are defined for a class derived from a :c:member:`"variable-length" built-in type ` such as - :class:`int`, :class:`bytes`, and :class:`tuple`. + :class:`int`, :class:`bytes`, and :class:`type`, except :class:`tuple`. * Any non-string :term:`iterable` may be assigned to *__slots__*. @@ -2658,6 +2658,7 @@ Notes on using *__slots__*: .. versionchanged:: next Allowed defining the *__dict__* and *__weakref__* *__slots__* for any class. + Allowed defining any *__slots__* for a class derived from :class:`tuple`. .. _class-customization: diff --git a/Doc/whatsnew/3.15.rst b/Doc/whatsnew/3.15.rst index d0af9212d55567..c02fa5bd956f30 100644 --- a/Doc/whatsnew/3.15.rst +++ b/Doc/whatsnew/3.15.rst @@ -398,6 +398,10 @@ Other language changes for any class. (Contributed by Serhiy Storchaka in :gh:`41779`.) +* Allowed defining any :ref:`__slots__ ` for a class derived from + :class:`tuple` (including classes created by :func:`collections.namedtuple`). + (Contributed by Serhiy Storchaka in :gh:`41779`.) + New modules =========== diff --git a/Include/descrobject.h b/Include/descrobject.h index fd66d17b497a31..eb1c12db369c2f 100644 --- a/Include/descrobject.h +++ b/Include/descrobject.h @@ -84,6 +84,7 @@ struct PyMemberDef { #define Py_AUDIT_READ 2 // Added in 3.10, harmless no-op before that #define _Py_WRITE_RESTRICTED 4 // Deprecated, no-op. Do not reuse the value. #define Py_RELATIVE_OFFSET 8 +#define _Py_AFTER_ITEMS 16 PyAPI_FUNC(PyObject *) PyMember_GetOne(const char *, PyMemberDef *); PyAPI_FUNC(int) PyMember_SetOne(char *, PyMemberDef *, PyObject *); diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py index 82a48ad4d1aced..0dc61ca7fb0da3 100644 --- a/Lib/test/test_descr.py +++ b/Lib/test/test_descr.py @@ -1320,6 +1320,18 @@ class X(object): with self.assertRaisesRegex(AttributeError, "'X' object has no attribute 'a'"): X().a + def test_slots_after_items(self): + class C(tuple): + __slots__ = ['a'] + x = C((1, 2, 3)) + self.assertNotHasAttr(x, "__dict__") + self.assertNotHasAttr(x, "a") + x.a = 42 + self.assertEqual(x.a, 42) + del x.a + self.assertNotHasAttr(x, "a") + self.assertEqual(x, (1, 2, 3)) + def test_slots_special(self): # Testing __dict__ and __weakref__ in __slots__... class D(object): @@ -1422,6 +1434,9 @@ class W(base): self.assertIs(weakref.ref(a)(), a) self.assertEqual(a, base(arg)) + @support.subTests('base', [int, bytes] + + ([_testcapi.HeapCCollection] if _testcapi else [])) + def test_unsupported_slots(self, base): with self.assertRaises(TypeError): class X(base): __slots__ = ['x'] diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2025-11-19-20-42-21.gh-issue-41779.Psz9Vo.rst b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-19-20-42-21.gh-issue-41779.Psz9Vo.rst new file mode 100644 index 00000000000000..16e546890c085b --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2025-11-19-20-42-21.gh-issue-41779.Psz9Vo.rst @@ -0,0 +1,3 @@ +Allowed defining any :ref:`__slots__ ` for a class derived from +:class:`tuple` (including classes created by +:func:`collections.namedtuple`). diff --git a/Objects/typeobject.c b/Objects/typeobject.c index 4c6ff51493f799..0a4d59b2bbe88e 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -2568,6 +2568,8 @@ _PyHeapType_GET_MEMBERS(PyHeapTypeObject* type) return PyObject_GetItemData((PyObject *)type); } +void *_PyMember_GetOffset(PyObject *obj, PyMemberDef *l); + static int traverse_slots(PyTypeObject *type, PyObject *self, visitproc visit, void *arg) { @@ -2578,7 +2580,7 @@ traverse_slots(PyTypeObject *type, PyObject *self, visitproc visit, void *arg) mp = _PyHeapType_GET_MEMBERS((PyHeapTypeObject *)type); for (i = 0; i < n; i++, mp++) { if (mp->type == Py_T_OBJECT_EX) { - char *addr = (char *)self + mp->offset; + void *addr = _PyMember_GetOffset(self, mp); PyObject *obj = *(PyObject **)addr; if (obj != NULL) { int err = visit(obj, arg); @@ -2653,7 +2655,7 @@ clear_slots(PyTypeObject *type, PyObject *self) mp = _PyHeapType_GET_MEMBERS((PyHeapTypeObject *)type); for (i = 0; i < n; i++, mp++) { if (mp->type == Py_T_OBJECT_EX && !(mp->flags & Py_READONLY)) { - char *addr = (char *)self + mp->offset; + void *addr = _PyMember_GetOffset(self, mp); PyObject *obj = *(PyObject **)addr; if (obj != NULL) { *(PyObject **)addr = NULL; @@ -4641,7 +4643,11 @@ type_new_descriptors(const type_new_ctx *ctx, PyTypeObject *type, PyObject *dict if (et->ht_slots != NULL) { PyMemberDef *mp = _PyHeapType_GET_MEMBERS(et); Py_ssize_t nslot = PyTuple_GET_SIZE(et->ht_slots); - if (ctx->base->tp_itemsize != 0) { + int after_items = (ctx->base->tp_itemsize != 0 && + !(ctx->base->tp_flags & Py_TPFLAGS_ITEMS_AT_END)); + if (ctx->base->tp_itemsize != 0 && + !(ctx->base->tp_flags & Py_TPFLAGS_TUPLE_SUBCLASS)) + { PyErr_Format(PyExc_TypeError, "arbitrary __slots__ not supported for subtype of '%s'", ctx->base->tp_name); @@ -4655,6 +4661,9 @@ type_new_descriptors(const type_new_ctx *ctx, PyTypeObject *type, PyObject *dict } mp->type = Py_T_OBJECT_EX; mp->offset = slotoffset; + if (after_items) { + mp->flags |= _Py_AFTER_ITEMS; + } /* __dict__ and __weakref__ are already filtered out */ assert(strcmp(mp->name, "__dict__") != 0); diff --git a/Python/specialize.c b/Python/specialize.c index 19433bc7a74319..381665676da511 100644 --- a/Python/specialize.c +++ b/Python/specialize.c @@ -139,6 +139,7 @@ _PyCode_Quicken(_Py_CODEUNIT *instructions, Py_ssize_t size, int enable_counters #define SPEC_FAIL_ATTR_METACLASS_OVERRIDDEN 34 #define SPEC_FAIL_ATTR_SPLIT_DICT 35 #define SPEC_FAIL_ATTR_DESCR_NOT_DEFERRED 36 +#define SPEC_FAIL_ATTR_SLOT_AFTER_ITEMS 37 /* Binary subscr and store subscr */ @@ -810,6 +811,10 @@ do_specialize_instance_load_attr(PyObject* owner, _Py_CODEUNIT* instr, PyObject* SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_EXPECTED_ERROR); return -1; } + if (dmem->flags & _Py_AFTER_ITEMS) { + SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_SLOT_AFTER_ITEMS); + return -1; + } if (dmem->flags & Py_AUDIT_READ) { SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_AUDITED_SLOT); return -1; @@ -1004,6 +1009,10 @@ _Py_Specialize_StoreAttr(_PyStackRef owner_st, _Py_CODEUNIT *instr, PyObject *na SPECIALIZATION_FAIL(STORE_ATTR, SPEC_FAIL_EXPECTED_ERROR); goto fail; } + if (dmem->flags & _Py_AFTER_ITEMS) { + SPECIALIZATION_FAIL(LOAD_ATTR, SPEC_FAIL_ATTR_SLOT_AFTER_ITEMS); + goto fail; + } if (dmem->flags & Py_READONLY) { SPECIALIZATION_FAIL(STORE_ATTR, SPEC_FAIL_ATTR_READ_ONLY); goto fail; diff --git a/Python/structmember.c b/Python/structmember.c index 574acf296157f3..d4a3f9e59a99dd 100644 --- a/Python/structmember.c +++ b/Python/structmember.c @@ -20,6 +20,17 @@ member_get_object(const char *addr, const char *obj_addr, PyMemberDef *l) return v; } +void * +_PyMember_GetOffset(PyObject *obj, PyMemberDef *mp) +{ + unsigned char *addr = (unsigned char *)obj + mp->offset; + if (mp->flags & _Py_AFTER_ITEMS) { + PyTypeObject *type = Py_TYPE(obj); + addr += _Py_SIZE_ROUND_UP(Py_SIZE(obj) * type->tp_itemsize, SIZEOF_VOID_P); + } + return addr; +} + PyObject * PyMember_GetOne(const char *obj_addr, PyMemberDef *l) { @@ -31,7 +42,7 @@ PyMember_GetOne(const char *obj_addr, PyMemberDef *l) return NULL; } - const char* addr = obj_addr + l->offset; + const void *addr = _PyMember_GetOffset((PyObject *)obj_addr, l); switch (l->type) { case Py_T_BOOL: v = PyBool_FromLong(FT_ATOMIC_LOAD_CHAR_RELAXED(*(char*)addr)); @@ -80,7 +91,7 @@ PyMember_GetOne(const char *obj_addr, PyMemberDef *l) v = PyUnicode_FromString((char*)addr); break; case Py_T_CHAR: { - char char_val = FT_ATOMIC_LOAD_CHAR_RELAXED(*addr); + char char_val = FT_ATOMIC_LOAD_CHAR_RELAXED(*(char*)addr); v = PyUnicode_FromStringAndSize(&char_val, 1); break; } @@ -151,10 +162,8 @@ PyMember_SetOne(char *addr, PyMemberDef *l, PyObject *v) return -1; } -#ifdef Py_GIL_DISABLED - PyObject *obj = (PyObject *) addr; -#endif - addr += l->offset; + PyObject *obj = (PyObject *)addr; + addr = _PyMember_GetOffset(obj, l); if ((l->flags & Py_READONLY)) { From b38b8b8b5095b8dc4217d996c6faf0f22d38e699 Mon Sep 17 00:00:00 2001 From: Serhiy Storchaka Date: Fri, 21 Nov 2025 18:39:20 +0200 Subject: [PATCH 2/2] Clean up. --- Include/descrobject.h | 13 ++++++++----- Include/internal/pycore_descrobject.h | 2 ++ Objects/typeobject.c | 3 +-- Python/structmember.c | 1 + 4 files changed, 12 insertions(+), 7 deletions(-) diff --git a/Include/descrobject.h b/Include/descrobject.h index eb1c12db369c2f..340de4e0e1e6ff 100644 --- a/Include/descrobject.h +++ b/Include/descrobject.h @@ -80,11 +80,14 @@ struct PyMemberDef { #define _Py_T_NONE 20 // Deprecated. Value is always None. /* Flags */ -#define Py_READONLY 1 -#define Py_AUDIT_READ 2 // Added in 3.10, harmless no-op before that -#define _Py_WRITE_RESTRICTED 4 // Deprecated, no-op. Do not reuse the value. -#define Py_RELATIVE_OFFSET 8 -#define _Py_AFTER_ITEMS 16 +#define Py_READONLY (1 << 0) +#define Py_AUDIT_READ (1 << 1) // Added in 3.10, harmless no-op before that +#define _Py_WRITE_RESTRICTED (1 << 2) // Deprecated, no-op. Do not reuse the value. +#define Py_RELATIVE_OFFSET (1 << 3) + +#ifndef Py_LIMITED_API +# define _Py_AFTER_ITEMS (1 << 4) // For internal use. +#endif PyAPI_FUNC(PyObject *) PyMember_GetOne(const char *, PyMemberDef *); PyAPI_FUNC(int) PyMember_SetOne(char *, PyMemberDef *, PyObject *); diff --git a/Include/internal/pycore_descrobject.h b/Include/internal/pycore_descrobject.h index 3cec59a68a3d2b..6143f82176a1f2 100644 --- a/Include/internal/pycore_descrobject.h +++ b/Include/internal/pycore_descrobject.h @@ -22,6 +22,8 @@ typedef propertyobject _PyPropertyObject; extern PyTypeObject _PyMethodWrapper_Type; +extern void *_PyMember_GetOffset(PyObject *, PyMemberDef *); + #ifdef __cplusplus } #endif diff --git a/Objects/typeobject.c b/Objects/typeobject.c index 0a4d59b2bbe88e..780aed2cb1cdf5 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -4,6 +4,7 @@ #include "pycore_abstract.h" // _PySequence_IterSearch() #include "pycore_call.h" // _PyObject_VectorcallTstate() #include "pycore_code.h" // CO_FAST_FREE +#include "pycore_descrobject.h" // _PyMember_GetOffset() #include "pycore_dict.h" // _PyDict_KeysSize() #include "pycore_function.h" // _PyFunction_GetVersionForCurrentState() #include "pycore_interpframe.h" // _PyInterpreterFrame @@ -2568,8 +2569,6 @@ _PyHeapType_GET_MEMBERS(PyHeapTypeObject* type) return PyObject_GetItemData((PyObject *)type); } -void *_PyMember_GetOffset(PyObject *obj, PyMemberDef *l); - static int traverse_slots(PyTypeObject *type, PyObject *self, visitproc visit, void *arg) { diff --git a/Python/structmember.c b/Python/structmember.c index d4a3f9e59a99dd..b88e13ac0462b8 100644 --- a/Python/structmember.c +++ b/Python/structmember.c @@ -3,6 +3,7 @@ #include "Python.h" #include "pycore_abstract.h" // _PyNumber_Index() +#include "pycore_descrobject.h" // _PyMember_GetOffset() #include "pycore_long.h" // _PyLong_IsNegative() #include "pycore_object.h" // _Py_TryIncrefCompare(), FT_ATOMIC_*() #include "pycore_critical_section.h"