Repository navigation
Argument Clinic does not increase NoneType refcount when returning NoneType from a function with no parameters #95007
Description
Bug report
/*[clinic input]
function -> NoneType
[clinic start generated code]*/will produce this function:
static PyObject *
function(PyObject *module, PyObject *Py_UNUSED(ignored))
{
return function_impl(module);
}while function_impl returns Py_None (as it should, if using NoneType return converter), refcount is not increased.
here is a working example of NoneType return converter:
/*[clinic input]
function -> NoneType
a: int
/
[clinic start generated code]*/static PyObject *
function(PyObject *module, PyObject *arg)
{
PyObject *return_value = NULL;
int a;
PyObject *_return_value;
a = _PyLong_AsInt(arg);
if (a == -1 && PyErr_Occurred()) {
goto exit;
}
_return_value = function_impl(module, a);
if (_return_value != Py_None) {
goto exit;
}
return_value = Py_None;
Py_INCREF(Py_None);
exit:
return return_value;
}Generation also fails when generating a function with a single object parameter.
It seems like the problem is with default_return_converter in clinic.py, being set to True
Activity
pythongh-95007: Remove the NoneType return converter
serhiy-storchaka commentedon Jul 19, 2022
Good catch. This converter is not used, so the bug was not exposed. And since it has dubious semantic (requires returning a weak reference to None on success), I think that it is better to remove it.
noamcohen97 commentedon Jul 19, 2022
How about we'll get rid of the callback return value, and use
PyErr_Occurred()to chose whether to returnNULLorPy_None?arhadthedev commentedon Jul 19, 2022
When I did the same in gh-91284, I found that
PyErr_Occurredtakes GIL. Currently (until nogil is implemented, at least) it's cheaper to deal withPyErr_Occurredonly onNULLreturned from a callback.gh-95007: Remove the NoneType return converter (GH-95019)
gh-95007: Remove the NoneType return converter from Argument Clinic D…
erlend-aasland commentedon Aug 1, 2022
Resolved with:
python/cpython#95007: Remove the NoneType return converter from Argum…
python/cpython#95007: Remove the NoneType return converter from Argum…