Issue #2534: speed up isinstance() and issubclass() by 50-70%, so as to

match Python 2.5 speed despite the __instancecheck__ / __subclasscheck__
mechanism. In the process, fix a bug where isinstance() and issubclass(),
when given a tuple of classes as second argument, were looking up
__instancecheck__ / __subclasscheck__ on the tuple rather than on each
type object.

Reviewed by Benjamin Peterson and Raymond Hettinger.

1 files changed, 3 insertions, 2 deletions

diff --git a/Python/errors.c b/Python/errors.c
index 9c9eb2f2b2..d7aac6d504 100644
--- a/Python/errors.c
+++ b/Python/errors.c
@@ -160,11 +160,12 @@ PyErr_GivenExceptionMatches(PyObject *err, PyObject *exc)
 		int res = 0;
 		PyObject *exception, *value, *tb;
 		PyErr_Fetch(&exception, &value, &tb);
-		res = PyObject_IsSubclass(err, exc);
+		/* PyObject_IsSubclass() can recurse and therefore is
+		   not safe (see test_bad_getattr in test.pickletester). */
+		res = PyType_IsSubtype((PyTypeObject *)err, (PyTypeObject *)exc);
 		/* This function must not fail, so print the error here */
 		if (res == -1) {
 			PyErr_WriteUnraisable(err);
-			/* issubclass did not succeed */
 			res = 0;
 		}
 		PyErr_Restore(exception, value, tb);