cpython/Objects/funcobject.c

/* Function object implementation */

#include "Python.h"
#include "code.h"
#include "eval.h"
#include "structmember.h"

PyObject *
PyFunction_New(PyObject *code, PyObject *globals)
{
    PyFunctionObject *op = PyObject_GC_New(PyFunctionObject,
                                        &PyFunction_Type);
    static PyObject *__name__ = 0;
    if (op != NULL) {
        PyObject *doc;
        PyObject *consts;
        PyObject *module;
        op->func_weakreflist = NULL;
        Py_INCREF(code);
        op->func_code = code;
        Py_INCREF(globals);
        op->func_globals = globals;
        op->func_name = ((PyCodeObject *)code)->co_name;
        Py_INCREF(op->func_name);
        op->func_defaults = NULL; /* No default arguments */
        op->func_kwdefaults = NULL; /* No keyword only defaults */
        op->func_closure = NULL;
        consts = ((PyCodeObject *)code)->co_consts;
        if (PyTuple_Size(consts) >= 1) {
            doc = PyTuple_GetItem(consts, 0);
            if (!PyUnicode_Check(doc))
                doc = Py_None;
        }
        else
            doc = Py_None;
        Py_INCREF(doc);
        op->func_doc = doc;
        op->func_dict = NULL;
        op->func_module = NULL;
        op->func_annotations = NULL;

        /* __module__: If module name is in globals, use it.
           Otherwise, use None.
        */
        if (!__name__) {
            __name__ = PyUnicode_InternFromString("__name__");
            if (!__name__) {
                Py_DECREF(op);
                return NULL;
            }
        }
        module = PyDict_GetItem(globals, __name__);
        if (module) {
            Py_INCREF(module);
            op->func_module = module;
        }
    }
    else
        return NULL;
    _PyObject_GC_TRACK(op);
    return (PyObject *)op;
}

PyObject *
PyFunction_GetCode(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_code;
}

PyObject *
PyFunction_GetGlobals(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_globals;
}

PyObject *
PyFunction_GetModule(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_module;
}

PyObject *
PyFunction_GetDefaults(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_defaults;
}

int
PyFunction_SetDefaults(PyObject *op, PyObject *defaults)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return -1;
    }
    if (defaults == Py_None)
        defaults = NULL;
    else if (defaults && PyTuple_Check(defaults)) {
        Py_INCREF(defaults);
    }
    else {
        PyErr_SetString(PyExc_SystemError, "non-tuple default args");
        return -1;
    }
    Py_XDECREF(((PyFunctionObject *) op) -> func_defaults);
    ((PyFunctionObject *) op) -> func_defaults = defaults;
    return 0;
}

PyObject *
PyFunction_GetKwDefaults(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_kwdefaults;
}

int
PyFunction_SetKwDefaults(PyObject *op, PyObject *defaults)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return -1;
    }
    if (defaults == Py_None)
        defaults = NULL;
    else if (defaults && PyDict_Check(defaults)) {
        Py_INCREF(defaults);
    }
    else {
        PyErr_SetString(PyExc_SystemError,
                        "non-dict keyword only default args");
        return -1;
    }
    Py_XDECREF(((PyFunctionObject *)op) -> func_kwdefaults);
    ((PyFunctionObject *) op) -> func_kwdefaults = defaults;
    return 0;
}

PyObject *
PyFunction_GetClosure(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_closure;
}

int
PyFunction_SetClosure(PyObject *op, PyObject *closure)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return -1;
    }
    if (closure == Py_None)
        closure = NULL;
    else if (PyTuple_Check(closure)) {
        Py_INCREF(closure);
    }
    else {
        PyErr_Format(PyExc_SystemError,
                     "expected tuple for closure, got '%.100s'",
                     closure->ob_type->tp_name);
        return -1;
    }
    Py_XDECREF(((PyFunctionObject *) op) -> func_closure);
    ((PyFunctionObject *) op) -> func_closure = closure;
    return 0;
}

PyObject *
PyFunction_GetAnnotations(PyObject *op)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return NULL;
    }
    return ((PyFunctionObject *) op) -> func_annotations;
}

int
PyFunction_SetAnnotations(PyObject *op, PyObject *annotations)
{
    if (!PyFunction_Check(op)) {
        PyErr_BadInternalCall();
        return -1;
    }
    if (annotations == Py_None)
        annotations = NULL;
    else if (annotations && PyDict_Check(annotations)) {
        Py_INCREF(annotations);
    }
    else {
        PyErr_SetString(PyExc_SystemError,
                        "non-dict annotations");
        return -1;
    }
    Py_XDECREF(((PyFunctionObject *)op) -> func_annotations);
    ((PyFunctionObject *) op) -> func_annotations = annotations;
    return 0;
}

/* Methods */

#define OFF(x) offsetof(PyFunctionObject, x)

static PyMemberDef func_memberlist[] = {
    {"__closure__",   T_OBJECT,     OFF(func_closure),
     RESTRICTED|READONLY},
    {"__doc__",       T_OBJECT,     OFF(func_doc), PY_WRITE_RESTRICTED},
    {"__globals__",   T_OBJECT,     OFF(func_globals),
     RESTRICTED|READONLY},
    {"__module__",    T_OBJECT,     OFF(func_module), PY_WRITE_RESTRICTED},
    {NULL}  /* Sentinel */
};

static PyObject *
func_get_dict(PyFunctionObject *op)
{
    if (op->func_dict == NULL) {
        op->func_dict = PyDict_New();
        if (op->func_dict == NULL)
            return NULL;
    }
    Py_INCREF(op->func_dict);
    return op->func_dict;
}

static int
func_set_dict(PyFunctionObject *op, PyObject *value)
{
    PyObject *tmp;

    /* It is illegal to del f.func_dict */
    if (value == NULL) {
        PyErr_SetString(PyExc_TypeError,
                        "function's dictionary may not be deleted");
        return -1;
    }
    /* Can only set func_dict to a dictionary */
    if (!PyDict_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "setting function's dictionary to a non-dict");
        return -1;
    }
    tmp = op->func_dict;
    Py_INCREF(value);
    op->func_dict = value;
    Py_XDECREF(tmp);
    return 0;
}

static PyObject *
func_get_code(PyFunctionObject *op)
{
    Py_INCREF(op->func_code);
    return op->func_code;
}

static int
func_set_code(PyFunctionObject *op, PyObject *value)
{
    PyObject *tmp;
    Py_ssize_t nfree, nclosure;

    /* Not legal to del f.func_code or to set it to anything
     * other than a code object. */
    if (value == NULL || !PyCode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "__code__ must be set to a code object");
        return -1;
    }
    nfree = PyCode_GetNumFree((PyCodeObject *)value);
    nclosure = (op->func_closure == NULL ? 0 :
            PyTuple_GET_SIZE(op->func_closure));
    if (nclosure != nfree) {
        PyErr_Format(PyExc_ValueError,
                     "%U() requires a code object with %zd free vars,"
                     " not %zd",
                     op->func_name,
                     nclosure, nfree);
        return -1;
    }
    tmp = op->func_code;
    Py_INCREF(value);
    op->func_code = value;
    Py_DECREF(tmp);
    return 0;
}

static PyObject *
func_get_name(PyFunctionObject *op)
{
    Py_INCREF(op->func_name);
    return op->func_name;
}

static int
func_set_name(PyFunctionObject *op, PyObject *value)
{
    PyObject *tmp;

    /* Not legal to del f.func_name or to set it to anything
     * other than a string object. */
    if (value == NULL || !PyUnicode_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "__name__ must be set to a string object");
        return -1;
    }
    tmp = op->func_name;
    Py_INCREF(value);
    op->func_name = value;
    Py_DECREF(tmp);
    return 0;
}

static PyObject *
func_get_defaults(PyFunctionObject *op)
{
    if (op->func_defaults == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    Py_INCREF(op->func_defaults);
    return op->func_defaults;
}

static int
func_set_defaults(PyFunctionObject *op, PyObject *value)
{
    PyObject *tmp;

    /* Legal to del f.func_defaults.
     * Can only set func_defaults to NULL or a tuple. */
    if (value == Py_None)
        value = NULL;
    if (value != NULL && !PyTuple_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
                        "__defaults__ must be set to a tuple object");
        return -1;
    }
    tmp = op->func_defaults;
    Py_XINCREF(value);
    op->func_defaults = value;
    Py_XDECREF(tmp);
    return 0;
}

static PyObject *
func_get_kwdefaults(PyFunctionObject *op)
{
    if (op->func_kwdefaults == NULL) {
        Py_INCREF(Py_None);
        return Py_None;
    }
    Py_INCREF(op->func_kwdefaults);
    return op->func_kwdefaults;
}

static int
func_set_kwdefaults(PyFunctionObject *op, PyObject *value)
{
    PyObject *tmp;

    if (value == Py_None)
        value = NULL;
    /* Legal to del f.func_kwdefaults.
     * Can only set func_kwdefaults to NULL or a dict. */
    if (value != NULL && !PyDict_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
            "__kwdefaults__ must be set to a dict object");
        return -1;
    }
    tmp = op->func_kwdefaults;
    Py_XINCREF(value);
    op->func_kwdefaults = value;
    Py_XDECREF(tmp);
    return 0;
}

static PyObject *
func_get_annotations(PyFunctionObject *op)
{
    if (op->func_annotations == NULL) {
        op->func_annotations = PyDict_New();
        if (op->func_annotations == NULL)
            return NULL;
    }
    Py_INCREF(op->func_annotations);
    return op->func_annotations;
}

static int
func_set_annotations(PyFunctionObject *op, PyObject *value)
{
    PyObject *tmp;

    if (value == Py_None)
        value = NULL;
    /* Legal to del f.func_annotations.
     * Can only set func_annotations to NULL (through C api)
     * or a dict. */
    if (value != NULL && !PyDict_Check(value)) {
        PyErr_SetString(PyExc_TypeError,
            "__annotations__ must be set to a dict object");
        return -1;
    }
    tmp = op->func_annotations;
    Py_XINCREF(value);
    op->func_annotations = value;
    Py_XDECREF(tmp);
    return 0;
}

static PyGetSetDef func_getsetlist[] = {
    {"__code__", (getter)func_get_code, (setter)func_set_code},
    {"__defaults__", (getter)func_get_defaults,
     (setter)func_set_defaults},
    {"__kwdefaults__", (getter)func_get_kwdefaults,
     (setter)func_set_kwdefaults},
    {"__annotations__", (getter)func_get_annotations,
     (setter)func_set_annotations},
    {"__dict__", (getter)func_get_dict, (setter)func_set_dict},
    {"__name__", (getter)func_get_name, (setter)func_set_name},
    {NULL} /* Sentinel */
};

PyDoc_STRVAR(func_doc,
"function(code, globals[, name[, argdefs[, closure]]])\n\
\n\
Create a function object from a code object and a dictionary.\n\
The optional name string overrides the name from the code object.\n\
The optional argdefs tuple specifies the default argument values.\n\
The optional closure tuple supplies the bindings for free variables.");

/* func_new() maintains the following invariants for closures.  The
   closure must correspond to the free variables of the code object.

   if len(code.co_freevars) == 0:
       closure = NULL
   else:
       len(closure) == len(code.co_freevars)
   for every elt in closure, type(elt) == cell
*/

static PyObject *
func_new(PyTypeObject* type, PyObject* args, PyObject* kw)
{
    PyCodeObject *code;
    PyObject *globals;
    PyObject *name = Py_None;
    PyObject *defaults = Py_None;
    PyObject *closure = Py_None;
    PyFunctionObject *newfunc;
    Py_ssize_t nfree, nclosure;
    static char *kwlist[] = {"code", "globals", "name",
                             "argdefs", "closure", 0};

    if (!PyArg_ParseTupleAndKeywords(args, kw, "O!O!|OOO:function",
                          kwlist,
                          &PyCode_Type, &code,
                          &PyDict_Type, &globals,
                          &name, &defaults, &closure))
        return NULL;
    if (name != Py_None && !PyUnicode_Check(name)) {
        PyErr_SetString(PyExc_TypeError,
                        "arg 3 (name) must be None or string");
        return NULL;
    }
    if (defaults != Py_None && !PyTuple_Check(defaults)) {
        PyErr_SetString(PyExc_TypeError,
                        "arg 4 (defaults) must be None or tuple");
        return NULL;
    }
    nfree = PyTuple_GET_SIZE(code->co_freevars);
    if (!PyTuple_Check(closure)) {
        if (nfree && closure == Py_None) {
            PyErr_SetString(PyExc_TypeError,
                            "arg 5 (closure) must be tuple");
            return NULL;
        }
        else if (closure != Py_None) {
            PyErr_SetString(PyExc_TypeError,
                "arg 5 (closure) must be None or tuple");
            return NULL;
        }
    }

    /* check that the closure is well-formed */
    nclosure = closure == Py_None ? 0 : PyTuple_GET_SIZE(closure);
    if (nfree != nclosure)
        return PyErr_Format(PyExc_ValueError,
                            "%U requires closure of length %zd, not %zd",
                            code->co_name, nfree, nclosure);
    if (nclosure) {
        Py_ssize_t i;
        for (i = 0; i < nclosure; i++) {
            PyObject *o = PyTuple_GET_ITEM(closure, i);
            if (!PyCell_Check(o)) {
                return PyErr_Format(PyExc_TypeError,
                    "arg 5 (closure) expected cell, found %s",
                                    o->ob_type->tp_name);
            }
        }
    }

    newfunc = (PyFunctionObject *)PyFunction_New((PyObject *)code,
                                                 globals);
    if (newfunc == NULL)
        return NULL;

    if (name != Py_None) {
        Py_INCREF(name);
        Py_DECREF(newfunc->func_name);
        newfunc->func_name = name;
    }
    if (defaults != Py_None) {
        Py_INCREF(defaults);
        newfunc->func_defaults  = defaults;
    }
    if (closure != Py_None) {
        Py_INCREF(closure);
        newfunc->func_closure = closure;
    }

    return (PyObject *)newfunc;
}

static void
func_dealloc(PyFunctionObject *op)
{
    _PyObject_GC_UNTRACK(op);
    if (op->func_weakreflist != NULL)
        PyObject_ClearWeakRefs((PyObject *) op);
    Py_DECREF(op->func_code);
    Py_DECREF(op->func_globals);
    Py_XDECREF(op->func_module);
    Py_DECREF(op->func_name);
    Py_XDECREF(op->func_defaults);
    Py_XDECREF(op->func_kwdefaults);
    Py_XDECREF(op->func_doc);
    Py_XDECREF(op->func_dict);
    Py_XDECREF(op->func_closure);
    Py_XDECREF(op->func_annotations);
    PyObject_GC_Del(op);
}

static PyObject*
func_repr(PyFunctionObject *op)
{
    return PyUnicode_FromFormat("<function %U at %p>",
                               op->func_name, op);
}

static int
func_traverse(PyFunctionObject *f, visitproc visit, void *arg)
{
    Py_VISIT(f->func_code);
    Py_VISIT(f->func_globals);
    Py_VISIT(f->func_module);
    Py_VISIT(f->func_defaults);
    Py_VISIT(f->func_kwdefaults);
    Py_VISIT(f->func_doc);
    Py_VISIT(f->func_name);
    Py_VISIT(f->func_dict);
    Py_VISIT(f->func_closure);
    Py_VISIT(f->func_annotations);
    return 0;
}

static PyObject *
function_call(PyObject *func, PyObject *arg, PyObject *kw)
{
    PyObject *result;
    PyObject *argdefs;
    PyObject *kwtuple = NULL;
    PyObject **d, **k;
    Py_ssize_t nk, nd;

    argdefs = PyFunction_GET_DEFAULTS(func);
    if (argdefs != NULL && PyTuple_Check(argdefs)) {
        d = &PyTuple_GET_ITEM((PyTupleObject *)argdefs, 0);
        nd = PyTuple_GET_SIZE(argdefs);
    }
    else {
        d = NULL;
        nd = 0;
    }

    if (kw != NULL && PyDict_Check(kw)) {
        Py_ssize_t pos, i;
        nk = PyDict_Size(kw);
        kwtuple = PyTuple_New(2*nk);
        if (kwtuple == NULL)
            return NULL;
        k = &PyTuple_GET_ITEM(kwtuple, 0);
        pos = i = 0;
        while (PyDict_Next(kw, &pos, &k[i], &k[i+1])) {
            Py_INCREF(k[i]);
            Py_INCREF(k[i+1]);
            i += 2;
        }
        nk = i/2;
    }
    else {
        k = NULL;
        nk = 0;
    }

    result = PyEval_EvalCodeEx(
        (PyCodeObject *)PyFunction_GET_CODE(func),
        PyFunction_GET_GLOBALS(func), (PyObject *)NULL,
        &PyTuple_GET_ITEM(arg, 0), PyTuple_GET_SIZE(arg),
        k, nk, d, nd,
        PyFunction_GET_KW_DEFAULTS(func),
        PyFunction_GET_CLOSURE(func));

    Py_XDECREF(kwtuple);

    return result;
}

/* Bind a function to an object */
static PyObject *
func_descr_get(PyObject *func, PyObject *obj, PyObject *type)
{
    if (obj == Py_None || obj == NULL) {
        Py_INCREF(func);
        return func;
    }
    return PyMethod_New(func, obj);
}

PyTypeObject PyFunction_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "function",
    sizeof(PyFunctionObject),
    0,
    (destructor)func_dealloc,                   /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_reserved */
    (reprfunc)func_repr,                        /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    function_call,                              /* tp_call */
    0,                                          /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    PyObject_GenericSetAttr,                    /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
    func_doc,                                   /* tp_doc */
    (traverseproc)func_traverse,                /* tp_traverse */
    0,                                          /* tp_clear */
    0,                                          /* tp_richcompare */
    offsetof(PyFunctionObject, func_weakreflist), /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    0,                                          /* tp_methods */
    func_memberlist,                            /* tp_members */
    func_getsetlist,                            /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    func_descr_get,                             /* tp_descr_get */
    0,                                          /* tp_descr_set */
    offsetof(PyFunctionObject, func_dict),      /* tp_dictoffset */
    0,                                          /* tp_init */
    0,                                          /* tp_alloc */
    func_new,                                   /* tp_new */
};


/* Class method object */

/* A class method receives the class as implicit first argument,
   just like an instance method receives the instance.
   To declare a class method, use this idiom:

     class C:
     def f(cls, arg1, arg2, ...): ...
     f = classmethod(f)

   It can be called either on the class (e.g. C.f()) or on an instance
   (e.g. C().f()); the instance is ignored except for its class.
   If a class method is called for a derived class, the derived class
   object is passed as the implied first argument.

   Class methods are different than C++ or Java static methods.
   If you want those, see static methods below.
*/

typedef struct {
    PyObject_HEAD
    PyObject *cm_callable;
} classmethod;

static void
cm_dealloc(classmethod *cm)
{
    _PyObject_GC_UNTRACK((PyObject *)cm);
    Py_XDECREF(cm->cm_callable);
    Py_TYPE(cm)->tp_free((PyObject *)cm);
}

static int
cm_traverse(classmethod *cm, visitproc visit, void *arg)
{
    Py_VISIT(cm->cm_callable);
    return 0;
}

static int
cm_clear(classmethod *cm)
{
    Py_CLEAR(cm->cm_callable);
    return 0;
}


static PyObject *
cm_descr_get(PyObject *self, PyObject *obj, PyObject *type)
{
    classmethod *cm = (classmethod *)self;

    if (cm->cm_callable == NULL) {
        PyErr_SetString(PyExc_RuntimeError,
                        "uninitialized classmethod object");
        return NULL;
    }
    if (type == NULL)
        type = (PyObject *)(Py_TYPE(obj));
    return PyMethod_New(cm->cm_callable, type);
}

static int
cm_init(PyObject *self, PyObject *args, PyObject *kwds)
{
    classmethod *cm = (classmethod *)self;
    PyObject *callable;

    if (!PyArg_UnpackTuple(args, "classmethod", 1, 1, &callable))
        return -1;
    if (!_PyArg_NoKeywords("classmethod", kwds))
        return -1;
    Py_INCREF(callable);
    cm->cm_callable = callable;
    return 0;
}

static PyMemberDef cm_memberlist[] = {
    {"__func__", T_OBJECT, offsetof(classmethod, cm_callable), READONLY},
    {NULL}  /* Sentinel */
};

PyDoc_STRVAR(classmethod_doc,
"classmethod(function) -> method\n\
\n\
Convert a function to be a class method.\n\
\n\
A class method receives the class as implicit first argument,\n\
just like an instance method receives the instance.\n\
To declare a class method, use this idiom:\n\
\n\
  class C:\n\
      def f(cls, arg1, arg2, ...): ...\n\
      f = classmethod(f)\n\
\n\
It can be called either on the class (e.g. C.f()) or on an instance\n\
(e.g. C().f()).  The instance is ignored except for its class.\n\
If a class method is called for a derived class, the derived class\n\
object is passed as the implied first argument.\n\
\n\
Class methods are different than C++ or Java static methods.\n\
If you want those, see the staticmethod builtin.");

PyTypeObject PyClassMethod_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "classmethod",
    sizeof(classmethod),
    0,
    (destructor)cm_dealloc,                     /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_reserved */
    0,                                          /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    0,                                          /* tp_call */
    0,                                          /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    0,                                          /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
    classmethod_doc,                            /* tp_doc */
    (traverseproc)cm_traverse,                  /* tp_traverse */
    (inquiry)cm_clear,                          /* tp_clear */
    0,                                          /* tp_richcompare */
    0,                                          /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    0,                                          /* tp_methods */
    cm_memberlist,              /* tp_members */
    0,                                          /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    cm_descr_get,                               /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    cm_init,                                    /* tp_init */
    PyType_GenericAlloc,                        /* tp_alloc */
    PyType_GenericNew,                          /* tp_new */
    PyObject_GC_Del,                            /* tp_free */
};

PyObject *
PyClassMethod_New(PyObject *callable)
{
    classmethod *cm = (classmethod *)
        PyType_GenericAlloc(&PyClassMethod_Type, 0);
    if (cm != NULL) {
        Py_INCREF(callable);
        cm->cm_callable = callable;
    }
    return (PyObject *)cm;
}


/* Static method object */

/* A static method does not receive an implicit first argument.
   To declare a static method, use this idiom:

     class C:
     def f(arg1, arg2, ...): ...
     f = staticmethod(f)

   It can be called either on the class (e.g. C.f()) or on an instance
   (e.g. C().f()); the instance is ignored except for its class.

   Static methods in Python are similar to those found in Java or C++.
   For a more advanced concept, see class methods above.
*/

typedef struct {
    PyObject_HEAD
    PyObject *sm_callable;
} staticmethod;

static void
sm_dealloc(staticmethod *sm)
{
    _PyObject_GC_UNTRACK((PyObject *)sm);
    Py_XDECREF(sm->sm_callable);
    Py_TYPE(sm)->tp_free((PyObject *)sm);
}

static int
sm_traverse(staticmethod *sm, visitproc visit, void *arg)
{
    Py_VISIT(sm->sm_callable);
    return 0;
}

static int
sm_clear(staticmethod *sm)
{
    Py_XDECREF(sm->sm_callable);
    sm->sm_callable = NULL;

    return 0;
}

static PyObject *
sm_descr_get(PyObject *self, PyObject *obj, PyObject *type)
{
    staticmethod *sm = (staticmethod *)self;

    if (sm->sm_callable == NULL) {
        PyErr_SetString(PyExc_RuntimeError,
                        "uninitialized staticmethod object");
        return NULL;
    }
    Py_INCREF(sm->sm_callable);
    return sm->sm_callable;
}

static int
sm_init(PyObject *self, PyObject *args, PyObject *kwds)
{
    staticmethod *sm = (staticmethod *)self;
    PyObject *callable;

    if (!PyArg_UnpackTuple(args, "staticmethod", 1, 1, &callable))
        return -1;
    if (!_PyArg_NoKeywords("staticmethod", kwds))
        return -1;
    Py_INCREF(callable);
    sm->sm_callable = callable;
    return 0;
}

static PyMemberDef sm_memberlist[] = {
    {"__func__", T_OBJECT, offsetof(staticmethod, sm_callable), READONLY},
    {NULL}  /* Sentinel */
};

PyDoc_STRVAR(staticmethod_doc,
"staticmethod(function) -> method\n\
\n\
Convert a function to be a static method.\n\
\n\
A static method does not receive an implicit first argument.\n\
To declare a static method, use this idiom:\n\
\n\
     class C:\n\
     def f(arg1, arg2, ...): ...\n\
     f = staticmethod(f)\n\
\n\
It can be called either on the class (e.g. C.f()) or on an instance\n\
(e.g. C().f()).  The instance is ignored except for its class.\n\
\n\
Static methods in Python are similar to those found in Java or C++.\n\
For a more advanced concept, see the classmethod builtin.");

PyTypeObject PyStaticMethod_Type = {
    PyVarObject_HEAD_INIT(&PyType_Type, 0)
    "staticmethod",
    sizeof(staticmethod),
    0,
    (destructor)sm_dealloc,                     /* tp_dealloc */
    0,                                          /* tp_print */
    0,                                          /* tp_getattr */
    0,                                          /* tp_setattr */
    0,                                          /* tp_reserved */
    0,                                          /* tp_repr */
    0,                                          /* tp_as_number */
    0,                                          /* tp_as_sequence */
    0,                                          /* tp_as_mapping */
    0,                                          /* tp_hash */
    0,                                          /* tp_call */
    0,                                          /* tp_str */
    PyObject_GenericGetAttr,                    /* tp_getattro */
    0,                                          /* tp_setattro */
    0,                                          /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE | Py_TPFLAGS_HAVE_GC,
    staticmethod_doc,                           /* tp_doc */
    (traverseproc)sm_traverse,                  /* tp_traverse */
    (inquiry)sm_clear,                          /* tp_clear */
    0,                                          /* tp_richcompare */
    0,                                          /* tp_weaklistoffset */
    0,                                          /* tp_iter */
    0,                                          /* tp_iternext */
    0,                                          /* tp_methods */
    sm_memberlist,              /* tp_members */
    0,                                          /* tp_getset */
    0,                                          /* tp_base */
    0,                                          /* tp_dict */
    sm_descr_get,                               /* tp_descr_get */
    0,                                          /* tp_descr_set */
    0,                                          /* tp_dictoffset */
    sm_init,                                    /* tp_init */
    PyType_GenericAlloc,                        /* tp_alloc */
    PyType_GenericNew,                          /* tp_new */
    PyObject_GC_Del,                            /* tp_free */
};

PyObject *
PyStaticMethod_New(PyObject *callable)
{
    staticmethod *sm = (staticmethod *)
        PyType_GenericAlloc(&PyStaticMethod_Type, 0);
    if (sm != NULL) {
        Py_INCREF(callable);
        sm->sm_callable = callable;
    }
    return (PyObject *)sm;
}