[Python-Dev] When does `PyType_Type.tp_alloc get assigned to PyType_GenericAlloc ? (original) (raw)

Randy Eels randyeels at gmail.com
Sun Feb 7 08:58:55 EST 2016

Hi everyone,

I've a question about the implementation of the type builtin (in Python 3.5).

In Objects/typeobject.c, the tp_alloc slot of PyType_Type gets set to 0. However, I can see (using gdb) that it later gets assigned to &PyType_GenericAlloc. I'd argue that this makes sense because, in type_new, there is a line where that member function gets called without previously checking whether that member points to something:

    /* Allocate the type object */
    type = (PyTypeObject *)metatype->tp_alloc(metatype, nslots);

Yet, I can't seem to understand where and when does the tp_alloc slot of PyType_Type get re-assigned to PyType_GenericAlloc. Does that even happen? Or am I missing something bigger?

And, just out of further curiosity, why doesn't the aforementioned slot get initialised to PyType_GenericAlloc in the first place?

Thanks a lot. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://mail.python.org/pipermail/python-dev/attachments/20160207/c26895a9/attachment-0001.html>

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