refcounting

[Simon Dahlbacka]

"Martin v. Löwis" <martin at v.loewis.de> wrote in message news:<c5ho92$89a$06$1 at news.t-online.com>...
> Simon Dahlbacka wrote:
> 
> > I'm a little confused about the reference counting..
> > 
> > static PyObject* MyFunction(PyObject * /*self*/, PyObject *args) {
> > 
> > PyObject *list;
> > PyArg_ParseTuple(args, &PyList_Type, &list);
> > 
> > //do stuff with list elements
> > 
> > // XXX do I need Py_INCREF(list); here ???
> > return list;
> 
> Yes. PyArg_ParseTuple returns a borrowed reference to the list; the
> reference is originally help by the argument tuple (which is immutable,
> so the reference is guaranteed to stay while you hold on to the argument
> tuple, which is only decrefed in the caller of MyFunction).
> 
> The result must be a new reference, so you must incref.
> 
> > PS. are there any documentation explaining the reference counting issues in
> > more detail than the docs @ python.org ?
> 
> No. For the specific issue, the documentation says it all:
> 
> http://docs.python.org/api/arg-parsing.html
> 
> says
> 
> "O" (object) [PyObject *] ... The object's reference count is not increased.
> 
> http://docs.python.org/api/common-structs.html#l2h-821
> 
> says
> 
> PyCFunction ... The function must return a new reference.

thanks for clarifying. Now I think that I understand (a bit more at
least)
Somehow I had managed to miss the common structs page (and especially
the part about "the function must return a new reference")

/Simon