That code is quite old. This comment tries to explain it: ``` /* Check that the use doesn't do something silly and unsafe like object.__new__(dict). To do this, we check that the most derived base that's not a heap type is this type. */ ``` I think you may have to special-case this and arrange for B.__new__() to be called, like it or not. (If you want us to change the code, please file a bpo bug report. I know that's no fun, but it's the way to get the right people involved.) On Mon, Feb 1, 2021 at 3:27 AM Phil Thompson via Python-Dev < python-dev@python.org> wrote:
Hi,
I'm trying to understand the purpose of the check in tp_new_wrapper() of typeobject.c that results in the "is not safe" exception.
I have the following class hierarchy...
B -> A -> object
...where B and A are implemented in C. Class A has an implementation of tp_new which does a few context-specific checks before calling PyBaseObject_Type.tp_new() directly to actually create the object. This works fine.
However I want to allow class B to be used with a Python mixin. A's tp_new() then has to do something similar to super().__new__(). I have tried to implement this by locating the type object after A in B's MRO, getting it's '__new__' attribute and calling it (using PyObject_Call()) with B passed as the only argument. However I then get the "is not safe" exception, specifically...
TypeError: object.__new__(B) is not safe, use B.__new__()
I take the same approach for __init__() and that works fine.
If I comment out the check in tp_new_wrapper() then everything works fine.
So, am I doing something unsafe? If so, what?
Or, is the check at fault in not allowing the case of a C extension type with its own tp_new?
Thanks, Phil _______________________________________________ Python-Dev mailing list -- python-dev@python.org To unsubscribe send an email to python-dev-leave@python.org https://mail.python.org/mailman3/lists/python-dev.python.org/ Message archived at https://mail.python.org/archives/list/python-dev@python.org/message/HRGDEMUR... Code of Conduct: http://python.org/psf/codeofconduct/
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