[issue9756] Crash with custom __getattribute__

STINNER Victor report at bugs.python.org
Sat Sep 4 00:08:26 CEST 2010

STINNER Victor <victor.stinner at haypocalc.com> added the comment:

>>> class Spam(object):
...     def __getattribute__(self, name):
...         if name == '__class__':
...             return str
...         raise AttributeError
>>> spam = Spam('spam')
>>> isinstance(spam, str)

isinstance(spam, str) calls str.__instancecheck__(spam) (type___instancecheck__) which checks spam.__class__, and spam.__class__ is str.


>>> import re
>>> re.match('spam', spam)
TypeError: expected string or buffer

Here the result is different because _sre.compile(spam) calls getstring() which uses PyUnicode_Check(spam) (-> False) and does checks on the buffer API (-> False).


About str.title(spam): it calls methoddescr_call() which checks the type using... PyObject_IsInstance() (and not PyUnicode_Check()).


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