diff options
Diffstat (limited to 'Lib/test/test_descr.py')
| -rw-r--r-- | Lib/test/test_descr.py | 227 |
1 files changed, 226 insertions, 1 deletions
diff --git a/Lib/test/test_descr.py b/Lib/test/test_descr.py index 26c273a..1de2a99 100644 --- a/Lib/test/test_descr.py +++ b/Lib/test/test_descr.py @@ -4996,11 +4996,236 @@ class SharedKeyTests(unittest.TestCase): self.assertLess(sys.getsizeof(vars(b)), sys.getsizeof({})) +class DebugHelperMeta(type): + """ + Sets default __doc__ and simplifies repr() output. + """ + def __new__(mcls, name, bases, attrs): + if attrs.get('__doc__') is None: + attrs['__doc__'] = name # helps when debugging with gdb + return type.__new__(mcls, name, bases, attrs) + def __repr__(cls): + return repr(cls.__name__) + + +class MroTest(unittest.TestCase): + """ + Regressions for some bugs revealed through + mcsl.mro() customization (typeobject.c: mro_internal()) and + cls.__bases__ assignment (typeobject.c: type_set_bases()). + """ + + def setUp(self): + self.step = 0 + self.ready = False + + def step_until(self, limit): + ret = (self.step < limit) + if ret: + self.step += 1 + return ret + + def test_incomplete_set_bases_on_self(self): + """ + type_set_bases must be aware that type->tp_mro can be NULL. + """ + class M(DebugHelperMeta): + def mro(cls): + if self.step_until(1): + assert cls.__mro__ is None + cls.__bases__ += () + + return type.mro(cls) + + class A(metaclass=M): + pass + + def test_reent_set_bases_on_base(self): + """ + Deep reentrancy must not over-decref old_mro. + """ + class M(DebugHelperMeta): + def mro(cls): + if cls.__mro__ is not None and cls.__name__ == 'B': + # 4-5 steps are usually enough to make it crash somewhere + if self.step_until(10): + A.__bases__ += () + + return type.mro(cls) + + class A(metaclass=M): + pass + class B(A): + pass + B.__bases__ += () + + def test_reent_set_bases_on_direct_base(self): + """ + Similar to test_reent_set_bases_on_base, but may crash differently. + """ + class M(DebugHelperMeta): + def mro(cls): + base = cls.__bases__[0] + if base is not object: + if self.step_until(5): + base.__bases__ += () + + return type.mro(cls) + + class A(metaclass=M): + pass + class B(A): + pass + class C(B): + pass + + def test_reent_set_bases_tp_base_cycle(self): + """ + type_set_bases must check for an inheritance cycle not only through + MRO of the type, which may be not yet updated in case of reentrance, + but also through tp_base chain, which is assigned before diving into + inner calls to mro(). + + Otherwise, the following snippet can loop forever: + do { + // ... + type = type->tp_base; + } while (type != NULL); + + Functions that rely on tp_base (like solid_base and PyType_IsSubtype) + would not be happy in that case, causing a stack overflow. + """ + class M(DebugHelperMeta): + def mro(cls): + if self.ready: + if cls.__name__ == 'B1': + B2.__bases__ = (B1,) + if cls.__name__ == 'B2': + B1.__bases__ = (B2,) + return type.mro(cls) + + class A(metaclass=M): + pass + class B1(A): + pass + class B2(A): + pass + + self.ready = True + with self.assertRaises(TypeError): + B1.__bases__ += () + + def test_tp_subclasses_cycle_in_update_slots(self): + """ + type_set_bases must check for reentrancy upon finishing its job + by updating tp_subclasses of old/new bases of the type. + Otherwise, an implicit inheritance cycle through tp_subclasses + can break functions that recurse on elements of that field + (like recurse_down_subclasses and mro_hierarchy) eventually + leading to a stack overflow. + """ + class M(DebugHelperMeta): + def mro(cls): + if self.ready and cls.__name__ == 'C': + self.ready = False + C.__bases__ = (B2,) + return type.mro(cls) + + class A(metaclass=M): + pass + class B1(A): + pass + class B2(A): + pass + class C(A): + pass + + self.ready = True + C.__bases__ = (B1,) + B1.__bases__ = (C,) + + self.assertEqual(C.__bases__, (B2,)) + self.assertEqual(B2.__subclasses__(), [C]) + self.assertEqual(B1.__subclasses__(), []) + + self.assertEqual(B1.__bases__, (C,)) + self.assertEqual(C.__subclasses__(), [B1]) + + def test_tp_subclasses_cycle_error_return_path(self): + """ + The same as test_tp_subclasses_cycle_in_update_slots, but tests + a code path executed on error (goto bail). + """ + class E(Exception): + pass + class M(DebugHelperMeta): + def mro(cls): + if self.ready and cls.__name__ == 'C': + if C.__bases__ == (B2,): + self.ready = False + else: + C.__bases__ = (B2,) + raise E + return type.mro(cls) + + class A(metaclass=M): + pass + class B1(A): + pass + class B2(A): + pass + class C(A): + pass + + self.ready = True + with self.assertRaises(E): + C.__bases__ = (B1,) + B1.__bases__ = (C,) + + self.assertEqual(C.__bases__, (B2,)) + self.assertEqual(C.__mro__, tuple(type.mro(C))) + + def test_incomplete_extend(self): + """ + Extending an unitialized type with type->tp_mro == NULL must + throw a reasonable TypeError exception, instead of failing + with PyErr_BadInternalCall. + """ + class M(DebugHelperMeta): + def mro(cls): + if cls.__mro__ is None and cls.__name__ != 'X': + with self.assertRaises(TypeError): + class X(cls): + pass + + return type.mro(cls) + + class A(metaclass=M): + pass + + def test_incomplete_super(self): + """ + Attrubute lookup on a super object must be aware that + its target type can be uninitialized (type->tp_mro == NULL). + """ + class M(DebugHelperMeta): + def mro(cls): + if cls.__mro__ is None: + with self.assertRaises(AttributeError): + super(cls, cls).xxx + + return type.mro(cls) + + class A(metaclass=M): + pass + + def test_main(): # Run all local test cases, with PTypesLongInitTest first. support.run_unittest(PTypesLongInitTest, OperatorsTest, ClassPropertiesAndMethods, DictProxyTests, - MiscTests, PicklingTests, SharedKeyTests) + MiscTests, PicklingTests, SharedKeyTests, + MroTest) if __name__ == "__main__": test_main() |