どのようにsuper()実装されていますか？python3.3 のコードは次のとおりです。
/* Cooperative 'super' */
typedef struct {
PyObject_HEAD
PyTypeObject *type;
PyObject *obj;
PyTypeObject *obj_type;
} superobject;
static PyMemberDef super_members[] = {
{"__thisclass__", T_OBJECT, offsetof(superobject, type), READONLY,
"the class invoking super()"},
{"__self__", T_OBJECT, offsetof(superobject, obj), READONLY,
"the instance invoking super(); may be None"},
{"__self_class__", T_OBJECT, offsetof(superobject, obj_type), READONLY,
"the type of the instance invoking super(); may be None"},
{0}
};
static void
super_dealloc(PyObject *self)
{
superobject *su = (superobject *)self;
_PyObject_GC_UNTRACK(self);
Py_XDECREF(su->obj);
Py_XDECREF(su->type);
Py_XDECREF(su->obj_type);
Py_TYPE(self)->tp_free(self);
}
static PyObject *
super_repr(PyObject *self)
{
superobject *su = (superobject *)self;
if (su->obj_type)
return PyUnicode_FromFormat(
"<super: <class '%s'>, <%s object>>",
su->type ? su->type->tp_name : "NULL",
su->obj_type->tp_name);
else
return PyUnicode_FromFormat(
"<super: <class '%s'>, NULL>",
su->type ? su->type->tp_name : "NULL");
}
static PyObject *
super_getattro(PyObject *self, PyObject *name)
{
superobject *su = (superobject *)self;
int skip = su->obj_type == NULL;
if (!skip) {
/* We want __class__ to return the class of the super object
(i.e. super, or a subclass), not the class of su->obj. */
skip = (PyUnicode_Check(name) &&
PyUnicode_GET_LENGTH(name) == 9 &&
PyUnicode_CompareWithASCIIString(name, "__class__") == 0);
}
if (!skip) {
PyObject *mro, *res, *tmp, *dict;
PyTypeObject *starttype;
descrgetfunc f;
Py_ssize_t i, n;
starttype = su->obj_type;
mro = starttype->tp_mro;
if (mro == NULL)
n = 0;
else {
assert(PyTuple_Check(mro));
n = PyTuple_GET_SIZE(mro);
}
for (i = 0; i < n; i++) {
if ((PyObject *)(su->type) == PyTuple_GET_ITEM(mro, i))
break;
}
i++;
res = NULL;
/* keep a strong reference to mro because starttype->tp_mro can be
replaced during PyDict_GetItem(dict, name) */
Py_INCREF(mro);
for (; i < n; i++) {
tmp = PyTuple_GET_ITEM(mro, i);
if (PyType_Check(tmp))
dict = ((PyTypeObject *)tmp)->tp_dict;
else
continue;
res = PyDict_GetItem(dict, name);
if (res != NULL) {
Py_INCREF(res);
f = Py_TYPE(res)->tp_descr_get;
if (f != NULL) {
tmp = f(res,
/* Only pass 'obj' param if
this is instance-mode super
(See SF ID #743627)
*/
(su->obj == (PyObject *)
su->obj_type
? (PyObject *)NULL
: su->obj),
(PyObject *)starttype);
Py_DECREF(res);
res = tmp;
}
Py_DECREF(mro);
return res;
}
}
Py_DECREF(mro);
}
return PyObject_GenericGetAttr(self, name);
}
static PyTypeObject *
supercheck(PyTypeObject *type, PyObject *obj)
{
/* Check that a super() call makes sense. Return a type object.
obj can be a class, or an instance of one:
- If it is a class, it must be a subclass of 'type'. This case is
used for class methods; the return value is obj.
- If it is an instance, it must be an instance of 'type'. This is
the normal case; the return value is obj.__class__.
But... when obj is an instance, we want to allow for the case where
Py_TYPE(obj) is not a subclass of type, but obj.__class__ is!
This will allow using super() with a proxy for obj.
*/
/* Check for first bullet above (special case) */
if (PyType_Check(obj) && PyType_IsSubtype((PyTypeObject *)obj, type)) {
Py_INCREF(obj);
return (PyTypeObject *)obj;
}
/* Normal case */
if (PyType_IsSubtype(Py_TYPE(obj), type)) {
Py_INCREF(Py_TYPE(obj));
return Py_TYPE(obj);
}
else {
/* Try the slow way */
PyObject *class_attr;
class_attr = _PyObject_GetAttrId(obj, &PyId___class__);
if (class_attr != NULL &&
PyType_Check(class_attr) &&
(PyTypeObject *)class_attr != Py_TYPE(obj))
{
int ok = PyType_IsSubtype(
(PyTypeObject *)class_attr, type);
if (ok)
return (PyTypeObject *)class_attr;
}
if (class_attr == NULL)
PyErr_Clear();
else
Py_DECREF(class_attr);
}
PyErr_SetString(PyExc_TypeError,
"super(type, obj): "
"obj must be an instance or subtype of type");
return NULL;
}
static PyObject *
super_descr_get(PyObject *self, PyObject *obj, PyObject *type)
{
superobject *su = (superobject *)self;
superobject *newobj;
if (obj == NULL || obj == Py_None || su->obj != NULL) {
/* Not binding to an object, or already bound */
Py_INCREF(self);
return self;
}
if (Py_TYPE(su) != &PySuper_Type)
/* If su is an instance of a (strict) subclass of super,
call its type */
return PyObject_CallFunctionObjArgs((PyObject *)Py_TYPE(su),
su->type, obj, NULL);
else {
/* Inline the common case */
PyTypeObject *obj_type = supercheck(su->type, obj);
if (obj_type == NULL)
return NULL;
newobj = (superobject *)PySuper_Type.tp_new(&PySuper_Type,
NULL, NULL);
if (newobj == NULL)
return NULL;
Py_INCREF(su->type);
Py_INCREF(obj);
newobj->type = su->type;
newobj->obj = obj;
newobj->obj_type = obj_type;
return (PyObject *)newobj;
}
}
static int
super_init(PyObject *self, PyObject *args, PyObject *kwds)
{
superobject *su = (superobject *)self;
PyTypeObject *type = NULL;
PyObject *obj = NULL;
PyTypeObject *obj_type = NULL;
if (!_PyArg_NoKeywords("super", kwds))
return -1;
if (!PyArg_ParseTuple(args, "|O!O:super", &PyType_Type, &type, &obj))
return -1;
if (type == NULL) {
/* Call super(), without args -- fill in from __class__
and first local variable on the stack. */
PyFrameObject *f = PyThreadState_GET()->frame;
PyCodeObject *co = f->f_code;
Py_ssize_t i, n;
if (co == NULL) {
PyErr_SetString(PyExc_SystemError,
"super(): no code object");
return -1;
}
if (co->co_argcount == 0) {
PyErr_SetString(PyExc_SystemError,
"super(): no arguments");
return -1;
}
obj = f->f_localsplus[0];
if (obj == NULL) {
PyErr_SetString(PyExc_SystemError,
"super(): arg[0] deleted");
return -1;
}
if (co->co_freevars == NULL)
n = 0;
else {
assert(PyTuple_Check(co->co_freevars));
n = PyTuple_GET_SIZE(co->co_freevars);
}
for (i = 0; i < n; i++) {
PyObject *name = PyTuple_GET_ITEM(co->co_freevars, i);
assert(PyUnicode_Check(name));
if (!PyUnicode_CompareWithASCIIString(name,
"__class__")) {
Py_ssize_t index = co->co_nlocals +
PyTuple_GET_SIZE(co->co_cellvars) + i;
PyObject *cell = f->f_localsplus[index];
if (cell == NULL || !PyCell_Check(cell)) {
PyErr_SetString(PyExc_SystemError,
"super(): bad __class__ cell");
return -1;
}
type = (PyTypeObject *) PyCell_GET(cell);
if (type == NULL) {
PyErr_SetString(PyExc_SystemError,
"super(): empty __class__ cell");
return -1;
}
if (!PyType_Check(type)) {
PyErr_Format(PyExc_SystemError,
"super(): __class__ is not a type (%s)",
Py_TYPE(type)->tp_name);
return -1;
}
break;
}
}
if (type == NULL) {
PyErr_SetString(PyExc_SystemError,
"super(): __class__ cell not found");
return -1;
}
}
if (obj == Py_None)
obj = NULL;
if (obj != NULL) {
obj_type = supercheck(type, obj);
if (obj_type == NULL)
return -1;
Py_INCREF(obj);
}
Py_INCREF(type);
su->type = type;
su->obj = obj;
su->obj_type = obj_type;
return 0;
}
PyDoc_STRVAR(super_doc,
"super() -> same as super(__class__, <first argument>)\n"
"super(type) -> unbound super object\n"
"super(type, obj) -> bound super object; requires isinstance(obj, type)\n"
"super(type, type2) -> bound super object; requires issubclass(type2, type)\n"
"Typical use to call a cooperative superclass method:\n"
"class C(B):\n"
" def meth(self, arg):\n"
" super().meth(arg)\n"
"This works for class methods too:\n"
"class C(B):\n"
" @classmethod\n"
" def cmeth(cls, arg):\n"
" super().cmeth(arg)\n");
static int
super_traverse(PyObject *self, visitproc visit, void *arg)
{
superobject *su = (superobject *)self;
Py_VISIT(su->obj);
Py_VISIT(su->type);
Py_VISIT(su->obj_type);
return 0;
}
PyTypeObject PySuper_Type = {
PyVarObject_HEAD_INIT(&PyType_Type, 0)
"super", /* tp_name */
sizeof(superobject), /* tp_basicsize */
0, /* tp_itemsize */
/* methods */
super_dealloc, /* tp_dealloc */
0, /* tp_print */
0, /* tp_getattr */
0, /* tp_setattr */
0, /* tp_reserved */
super_repr, /* tp_repr */
0, /* tp_as_number */
0, /* tp_as_sequence */
0, /* tp_as_mapping */
0, /* tp_hash */
0, /* tp_call */
0, /* tp_str */
super_getattro, /* tp_getattro */
0, /* tp_setattro */
0, /* tp_as_buffer */
Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC |
Py_TPFLAGS_BASETYPE, /* tp_flags */
super_doc, /* tp_doc */
super_traverse, /* tp_traverse */
0, /* tp_clear */
0, /* tp_richcompare */
0, /* tp_weaklistoffset */
0, /* tp_iter */
0, /* tp_iternext */
0, /* tp_methods */
super_members, /* tp_members */
0, /* tp_getset */
0, /* tp_base */
0, /* tp_dict */
super_descr_get, /* tp_descr_get */
0, /* tp_descr_set */
0, /* tp_dictoffset */
super_init, /* tp_init */
PyType_GenericAlloc, /* tp_alloc */
PyType_GenericNew, /* tp_new */
PyObject_GC_Del, /* tp_free */
};
super_initある時点でチェックが行われ、type == NULL表示されるエラーが発生することがわかります。NULL周りに sがあるのは普通ではないので、おそらくどこかにバグがあります (そして、以前のリリースにはすでにバグがあったsuperことに注意してください)。super少なくとも、発生するケースはSystemError、Python コードではなく、インタープリターまたはその他の C コードの「内部」障害が原因でのみトリガーされるべきだと考えていました。
また、これはあなただけに起こったのではなく、この動作がバグと見なされる投稿を見つけることができます。