Trying to create a new type for python

Question

I am trying to create a new type for python (2.5). I am trying to follow: python's documentation, however i am unable to compile the basic bit:

#include <Python.h>

typedef struct {
    PyObject_HEAD
    /* Type-specific fields go here. */
} noddy_NoddyObject;

static PyTypeObject noddy_NoddyType = {
    PyVarObject_HEAD_INIT(NULL, 0)
    "noddy.Noddy",             /* tp_name */
    sizeof(noddy_NoddyObject), /* tp_basicsize */
    0,                         /* tp_itemsize */
    0,                         /* tp_dealloc */
    0,                         /* tp_print */
    0,                         /* tp_getattr */
    0,                         /* tp_setattr */
    0,                         /* tp_compare */
    0,                         /* tp_repr */
    0,                         /* tp_as_number */
    0,                         /* tp_as_sequence */
    0,                         /* tp_as_mapping */
    0,                         /* tp_hash */
    0,                         /* tp_call */
    0,                         /* tp_str */
    0,                         /* tp_getattro */
    0,                         /* tp_setattro */
    0,                         /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT,        /* tp_flags */
    "Noddy objects",           /* tp_doc */
};

static PyMethodDef noddy_methods[] = {
    {NULL}  /* Sentinel */
};

#ifndef PyMODINIT_FUNC  /* declarations for DLL import/export */
#define PyMODINIT_FUNC void
#endif
PyMODINIT_FUNC
initnoddy(void) 
{
    PyObject* m;

    noddy_NoddyType.tp_new = PyType_GenericNew;
    if (PyType_Ready(&noddy_NoddyType) < 0)
        return;

    m = Py_InitModule3("noddy", noddy_methods,
                       "Example module that creates an extension type.");

    Py_INCREF(&noddy_NoddyType);
    PyModule_AddObject(m, "Noddy", (PyObject *)&noddy_NoddyType);
}

I am getting:

18: error: initializer element is not constant
18: error: (near initialization for `ConnectionType.ob_refcnt')
18: error: parse error before string constant
18: warning: initialization makes pointer from integer without a cast
34: warning: initialization makes pointer from integer without a cast
35: warning: initialization from incompatible pointer type

Those lines match the ones that are not 0 in the type definition. What am i doing wrong? Is that a problem with python versions? (Docs say that applies for 2.2+). Am I messing up with copy paste?

Answer 1

The wrong documentation is the key here. Python 2.5 does not have PyVarObject_HEAD_INIT macro. Instead it is assumed as an implicit function declaration, and a call to function, whose return value is used to initialize the structure member; this also is not a terminated expression, which causes a "parse error before string constant", because a , is missing.

Follow the Python 2.5 documentation for Python 2.5:

static PyTypeObject noddy_NoddyType = {
    PyObject_HEAD_INIT(NULL)
    0,                         /*ob_size*/
    "noddy.Noddy",             /*tp_name*/

P.s. you might want to consider hacking some extra warning flags to the compiler command line...