can't pass less or more than 2 args for methods passing to array of PyMethodDef

Question

I am following this doc on extending c++ to python. As far as what was demonstrated there, the PyObject *spam_system(PyObject *self, PyObject *args) {...} works fine when passing to array of PyModuleDef but if I want to add more args to spam_system, it results in an invaid conversation following

error: invalid conversion from ‘PyObject* (*)()’ {aka ‘_object* (*)()’} to ‘PyCFunction’ {aka ‘_object* (*)(_object*, _object*)’} [-fpermissive]

for more example, I want to define a method that takes no args, and returns a PyLong_FromLong from long/int

PyObject test() {return PyLong_FromLong(1);}

static PyMethodDef SpamMethods[] = {
    {"system",  spam_system, METH_VARARGS,
     "Execute a shell command."},
    {"test",  test , METH_NOARGS,
              //^ the error happens here 
     "test."},

   {NULL, NULL, 0, NULL}        /* Sentinel */
};

How can I define a method that takes no args or more than two args? (adding two args to test works fine).

Answer 1

Since it's C++, which is more strict about function pointer casting than C, you'll have to cast to (PyCFunction), or, IIRC, (void*) also works.