[Python-Dev] METH_NOARGS calling convention

M.-A. Lemburg mal@lemburg.com
Fri, 01 Jun 2001 19:18:21 +0200

Martin von Loewis wrote:
> The patch
> http://sourceforge.net/tracker/?func=detail&atid=305470&aid=427190&group_id=5470
> introduces two new calling conventions, METH_O and METH_NOARGS. The
> rationale for METH_O has been discussed already; the rationale for
> METH_NOARGS is that it allows a convient simplification (plus a
> marginal speed-up) of functions which do either PyArg_NoArgs(args) or
> PyArg_ParseTuple(args, ":function_name").
> Now, one open issue is whether the METH_NOARGS functions should have
> a signature of
>   PyObject * (*unaryfunc)(PyObject *);
> or of
>   PyObject *(*PyCFunction)(PyObject *, PyObject *);
> which then would be called with a NULL second argument; the first
> argument would be self in either case.
> IMO, the advantage of passing the NULL argument is that NOARGS methods
> don't need to be cast into PyCFunction in the method table; the
> advantage of the second approach is that it is clearer in the function
> implementation.
> Any opinions which signature to use?

The second...

I'm not sure how you will get extension writers who
have to maintain packages for all three Python versions to
ever change their code to use the new style calling scheme:
there simply is no clean way to use the same code base unless
you are willing to add tons of #ifdefs.

Marc-Andre Lemburg
CEO eGenix.com Software GmbH
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