[Python-Dev] Status of the Argument Clinic DSL

[eryk sun]

On Thu, Aug 4, 2016 at 11:33 PM, Alexander Belopolsky
<alexander.belopolsky at gmail.com> wrote:
>
> On Thu, Aug 4, 2016 at 7:12 PM, Larry Hastings <larry at hastings.org> wrote:
>>
>> C extension functions get the module passed in automatically, but this is
>> done internally and from the Python level you can't see it.
>
> Always something new to learn!  This was not so in Python 2.x - self was
> passed as NULL to the C module functions.  When did this change?

In 2.x this is the `self` parameter (actually named "passthrough" in
the source) of Py_InitModule4 [1, 2]. You probably use the
Py_InitModule or Py_InitModule3 macros, which pass NULL for this
parameter:

    #define Py_InitModule(name, methods) \
        Py_InitModule4(name, methods, (char *)NULL, (PyObject *)NULL, \
                   PYTHON_API_VERSION)

    #define Py_InitModule3(name, methods, doc) \
        Py_InitModule4(name, methods, doc, (PyObject *)NULL, \
                   PYTHON_API_VERSION)

Python 3's PyModule_Create2 [3-5] API makes this a reference to the
module. It's currently implemented in
PyModule_AddFunctions [6, 7].

[1]: https://docs.python.org/2/c-api/allocation.html#c.Py_InitModule4
[2]: https://hg.python.org/cpython/file/v2.7.12/Python/modsupport.c#l31
[3]: https://docs.python.org/3/c-api/module.html#c.PyModule_Create2
[4]: https://hg.python.org/cpython/file/v3.5.2/Objects/moduleobject.c#l133
[5]: https://hg.python.org/cpython/file/v3.0b1/Objects/moduleobject.c#l63
[6]: https://docs.python.org/3/c-api/module.html#c.PyModule_AddFunctions
[7]: https://hg.python.org/cpython/file/v3.5.2/Objects/moduleobject.c#l387