Address SF patch #480716 as well as related issues.
SF patch #480716 by Greg Chapman fixes the problem that super's
__get__ method always returns an instance of super, even when the
instance whose __get__ method is called is an instance of a subclass
of super.
Other issues fixed:
- super(C, C()).__class__ would return the __class__ attribute of C()
rather than the __class__ attribute of the super object. This is
confusing. To fix this, I decided to change the semantics of super
so that it only applies to code attributes, not to data attributes.
After all, overriding data attributes is not supported anyway.
- While super(C, x) carefully checked that x is an instance of C,
super(C).__get__(x) made no such check, allowing for a loophole.
This is now fixed.
diff --git a/Objects/typeobject.c b/Objects/typeobject.c
index c79636d..6fc5d02 100644
--- a/Objects/typeobject.c
+++ b/Objects/typeobject.c
@@ -3929,7 +3929,7 @@
else
continue;
res = PyDict_GetItem(dict, name);
- if (res != NULL) {
+ if (res != NULL && !PyDescr_IsData(res)) {
Py_INCREF(res);
f = res->ob_type->tp_descr_get;
if (f != NULL) {
@@ -3944,6 +3944,21 @@
return PyObject_GenericGetAttr(self, name);
}
+static int
+supercheck(PyTypeObject *type, PyObject *obj)
+{
+ if (!PyType_IsSubtype(obj->ob_type, type) &&
+ !(PyType_Check(obj) &&
+ PyType_IsSubtype((PyTypeObject *)obj, type))) {
+ PyErr_SetString(PyExc_TypeError,
+ "super(type, obj): "
+ "obj must be an instance or subtype of type");
+ return -1;
+ }
+ else
+ return 0;
+}
+
static PyObject *
super_descr_get(PyObject *self, PyObject *obj, PyObject *type)
{
@@ -3955,14 +3970,25 @@
Py_INCREF(self);
return self;
}
- new = (superobject *)PySuper_Type.tp_new(&PySuper_Type, NULL, NULL);
- if (new == NULL)
- return NULL;
- Py_INCREF(su->type);
- Py_INCREF(obj);
- new->type = su->type;
- new->obj = obj;
- return (PyObject *)new;
+ if (su->ob_type != &PySuper_Type)
+ /* If su is an instance of a subclass of super,
+ call its type */
+ return PyObject_CallFunction((PyObject *)su->ob_type,
+ "OO", su->type, obj);
+ else {
+ /* Inline the common case */
+ if (supercheck(su->type, obj) < 0)
+ return NULL;
+ new = (superobject *)PySuper_Type.tp_new(&PySuper_Type,
+ NULL, NULL);
+ if (new == NULL)
+ return NULL;
+ Py_INCREF(su->type);
+ Py_INCREF(obj);
+ new->type = su->type;
+ new->obj = obj;
+ return (PyObject *)new;
+ }
}
static int
@@ -3976,15 +4002,8 @@
return -1;
if (obj == Py_None)
obj = NULL;
- if (obj != NULL &&
- !PyType_IsSubtype(obj->ob_type, type) &&
- !(PyType_Check(obj) &&
- PyType_IsSubtype((PyTypeObject *)obj, type))) {
- PyErr_SetString(PyExc_TypeError,
- "super(type, obj): "
- "obj must be an instance or subtype of type");
+ if (obj != NULL && supercheck(type, obj) < 0)
return -1;
- }
Py_INCREF(type);
Py_XINCREF(obj);
su->type = type;