Enhance issubclass() and PyObject_IsSubclass() so that a tuple is
supported as the second argument. This has the same meaning as
for isinstance(), i.e. issubclass(X, (A, B)) is equivalent
to issubclass(X, A) or issubclass(X, B). Compared to isinstance(),
this patch does not search the tuple recursively for classes, i.e.
any entry in the tuple that is not a class, will result in a
TypeError.
This closes SF patch #649608.
diff --git a/Objects/abstract.c b/Objects/abstract.c
index e77cde3..47d2f31 100644
--- a/Objects/abstract.c
+++ b/Objects/abstract.c
@@ -1914,6 +1914,15 @@
if (derived == cls)
return 1;
+ if (PyTuple_Check(cls)) {
+ /* Not a general sequence -- that opens up the road to
+ recursion and stack overflow. */
+ n = PyTuple_GET_SIZE(cls);
+ for (i = 0; i < n; i++) {
+ if (derived == PyTuple_GET_ITEM(cls, i))
+ return 1;
+ }
+ }
bases = abstract_get_bases(derived);
if (bases == NULL) {
if (PyErr_Occurred())
@@ -1932,6 +1941,20 @@
return r;
}
+static int
+check_class(PyObject *cls, const char *error)
+{
+ PyObject *bases = abstract_get_bases(cls);
+ if (bases == NULL) {
+ /* Do not mask errors. */
+ if (!PyErr_Occurred())
+ PyErr_SetString(PyExc_TypeError, error);
+ return 0;
+ }
+ Py_DECREF(bases);
+ return -1;
+}
+
int
PyObject_IsInstance(PyObject *inst, PyObject *cls)
{
@@ -1962,16 +1985,10 @@
return retval;
}
else {
- PyObject *cls_bases = abstract_get_bases(cls);
- if (cls_bases == NULL) {
- /* Do not mask errors. */
- if (!PyErr_Occurred())
- PyErr_SetString(PyExc_TypeError,
- "isinstance() arg 2 must be a class, type,"
- " or tuple of classes and types");
+ if (!check_class(cls,
+ "isinstance() arg 2 must be a class, type,"
+ " or tuple of classes and types"))
return -1;
- }
- Py_DECREF(cls_bases);
if (__class__ == NULL) {
__class__ = PyString_FromString("__class__");
if (__class__ == NULL)
@@ -1997,28 +2014,25 @@
int retval;
if (!PyClass_Check(derived) || !PyClass_Check(cls)) {
- PyObject *derived_bases;
- PyObject *cls_bases;
-
- derived_bases = abstract_get_bases(derived);
- if (derived_bases == NULL) {
- /* Do not mask errors */
- if (!PyErr_Occurred())
- PyErr_SetString(PyExc_TypeError,
- "issubclass() arg 1 must be a class");
+ if (!check_class(derived, "issubclass() arg 1 must be a class"))
return -1;
- }
- Py_DECREF(derived_bases);
- cls_bases = abstract_get_bases(cls);
- if (cls_bases == NULL) {
- /* Do not mask errors */
- if (!PyErr_Occurred())
- PyErr_SetString(PyExc_TypeError,
- "issubclass() arg 2 must be a class");
- return -1;
+ if (PyTuple_Check(cls)) {
+ int i;
+ int n = PyTuple_GET_SIZE(cls);
+ for (i = 0; i < n; ++i) {
+ if (!check_class(PyTuple_GET_ITEM(cls, i),
+ "issubclass() arg 2 must be a class"
+ " or tuple of classes"))
+ return -1;
+ }
}
- Py_DECREF(cls_bases);
+ else {
+ if (!check_class(cls,
+ "issubclass() arg 2 must be a class"
+ " or tuple of classes"))
+ return -1;
+ }
retval = abstract_issubclass(derived, cls);
}