diff options
| -rw-r--r-- | Include/cpython/object.h | 12 | ||||
| -rw-r--r-- | Lib/test/test_metaclass.py | 27 | ||||
| -rw-r--r-- | Misc/NEWS.d/next/Core_and_Builtins/2024-12-13-15-21-45.gh-issue-127773.E-DZR4.rst | 1 | ||||
| -rw-r--r-- | Objects/typeobject.c | 12 |
4 files changed, 50 insertions, 2 deletions
diff --git a/Include/cpython/object.h b/Include/cpython/object.h index e479702..c8c6bc9 100644 --- a/Include/cpython/object.h +++ b/Include/cpython/object.h @@ -221,7 +221,9 @@ struct _typeobject { PyObject *tp_weaklist; /* not used for static builtin types */ destructor tp_del; - /* Type attribute cache version tag. Added in version 2.6 */ + /* Type attribute cache version tag. Added in version 2.6. + * If zero, the cache is invalid and must be initialized. + */ unsigned int tp_version_tag; destructor tp_finalize; @@ -229,9 +231,17 @@ struct _typeobject { /* bitset of which type-watchers care about this type */ unsigned char tp_watched; + + /* Number of tp_version_tag values used. + * Set to _Py_ATTR_CACHE_UNUSED if the attribute cache is + * disabled for this type (e.g. due to custom MRO entries). + * Otherwise, limited to MAX_VERSIONS_PER_CLASS (defined elsewhere). + */ uint16_t tp_versions_used; }; +#define _Py_ATTR_CACHE_UNUSED (30000) // (see tp_versions_used) + /* This struct is used by the specializer * It should be treated as an opaque blob * by code other than the specializer and interpreter. */ diff --git a/Lib/test/test_metaclass.py b/Lib/test/test_metaclass.py index b37b7de..07a333f 100644 --- a/Lib/test/test_metaclass.py +++ b/Lib/test/test_metaclass.py @@ -254,6 +254,33 @@ Test failures in looking up the __prepare__ method work. [...] test.test_metaclass.ObscureException +Test setting attributes with a non-base type in mro() (gh-127773). + + >>> class Base: + ... value = 1 + ... + >>> class Meta(type): + ... def mro(cls): + ... return (cls, Base, object) + ... + >>> class WeirdClass(metaclass=Meta): + ... pass + ... + >>> Base.value + 1 + >>> WeirdClass.value + 1 + >>> Base.value = 2 + >>> Base.value + 2 + >>> WeirdClass.value + 2 + >>> Base.value = 3 + >>> Base.value + 3 + >>> WeirdClass.value + 3 + """ import sys diff --git a/Misc/NEWS.d/next/Core_and_Builtins/2024-12-13-15-21-45.gh-issue-127773.E-DZR4.rst b/Misc/NEWS.d/next/Core_and_Builtins/2024-12-13-15-21-45.gh-issue-127773.E-DZR4.rst new file mode 100644 index 0000000..7e68b3f --- /dev/null +++ b/Misc/NEWS.d/next/Core_and_Builtins/2024-12-13-15-21-45.gh-issue-127773.E-DZR4.rst @@ -0,0 +1 @@ +Do not use the type attribute cache for types with incompatible :term:`MRO`. diff --git a/Objects/typeobject.c b/Objects/typeobject.c index 0f5ebc6..d8f5f6d 100644 --- a/Objects/typeobject.c +++ b/Objects/typeobject.c @@ -992,6 +992,7 @@ static void set_version_unlocked(PyTypeObject *tp, unsigned int version) { ASSERT_TYPE_LOCK_HELD(); + assert(version == 0 || (tp->tp_versions_used != _Py_ATTR_CACHE_UNUSED)); #ifndef Py_GIL_DISABLED PyInterpreterState *interp = _PyInterpreterState_GET(); // lookup the old version and set to null @@ -1148,6 +1149,10 @@ type_mro_modified(PyTypeObject *type, PyObject *bases) { PyObject *b = PyTuple_GET_ITEM(bases, i); PyTypeObject *cls = _PyType_CAST(b); + if (cls->tp_versions_used >= _Py_ATTR_CACHE_UNUSED) { + goto clear; + } + if (!is_subtype_with_mro(lookup_tp_mro(type), type, cls)) { goto clear; } @@ -1156,7 +1161,8 @@ type_mro_modified(PyTypeObject *type, PyObject *bases) { clear: assert(!(type->tp_flags & _Py_TPFLAGS_STATIC_BUILTIN)); - set_version_unlocked(type, 0); /* 0 is not a valid version tag */ + set_version_unlocked(type, 0); /* 0 is not a valid version tag */ + type->tp_versions_used = _Py_ATTR_CACHE_UNUSED; if (PyType_HasFeature(type, Py_TPFLAGS_HEAPTYPE)) { // This field *must* be invalidated if the type is modified (see the // comment on struct _specialization_cache): @@ -1208,6 +1214,9 @@ _PyType_GetVersionForCurrentState(PyTypeObject *tp) #define MAX_VERSIONS_PER_CLASS 1000 +#if _Py_ATTR_CACHE_UNUSED < MAX_VERSIONS_PER_CLASS +#error "_Py_ATTR_CACHE_UNUSED must be bigger than max" +#endif static int assign_version_tag(PyInterpreterState *interp, PyTypeObject *type) @@ -1225,6 +1234,7 @@ assign_version_tag(PyInterpreterState *interp, PyTypeObject *type) return 0; } if (type->tp_versions_used >= MAX_VERSIONS_PER_CLASS) { + /* (this includes `tp_versions_used == _Py_ATTR_CACHE_UNUSED`) */ return 0; } |