handle errors from _PyObject_LookupSpecial when __get__ fails

Lib/test/test_descr.py

@@ -1722,7 +1722,11 @@ order (MRO) for bases """
             def __get__(self, obj, owner):
                 record.append(1)
                 return self.impl.__get__(obj, owner)
-
+        class MyException(Exception):
+            pass
+        class ErrDescr(object):
+            def __get__(self, obj, owner):
+                raise MyException
 
         for name, runner, meth_impl, ok, env in specials:
             class X(Checker):
@@ -1741,6 +1745,18 @@ order (MRO) for bases """
             runner(X())
             self.assertEqual(record, [1], name)
 
+            class X(Checker):
+                pass
+            for attr, obj in env.iteritems():
+                setattr(X, attr, obj)
+            setattr(X, name, ErrDescr())
+            try:
+                runner(X())
+            except MyException:
+                pass
+            else:
+                self.fail("{0!r} didn't raise".format(name))
+
     def test_specials(self):
         # Testing special operators...
         # Test operators like __hash__ for which a built-in default exists

Objects/abstract.c

@@ -111,8 +111,12 @@ _PyObject_LengthHint(PyObject *o, Py_ssize_t defaultvalue)
 		return defaultvalue;
 	/* try o.__length_hint__() */
         hintmeth = _PyObject_LookupSpecial(o, "__length_hint__", &hintstrobj);
-	if (hintmeth == NULL)
+	if (hintmeth == NULL) {
+		if (PyErr_Occurred())
+			return -1;
+		else
 			return defaultvalue;
+	}
 	ro = PyObject_CallFunctionObjArgs(hintmeth, NULL);
 	Py_DECREF(hintmeth);
 	if (ro == NULL) {
@@ -2945,6 +2949,8 @@ PyObject_IsInstance(PyObject *inst, PyObject *cls)
 			}
 			return ok;
 		}
+		else if (PyErr_Occurred())
+			return -1;
 	}
 	return recursive_isinstance(inst, cls);
 }
@@ -3021,6 +3027,9 @@ PyObject_IsSubclass(PyObject *derived, PyObject *cls)
 			}
 			return ok;
 		}
+		else if (PyErr_Occurred()) {
+			return -1;
+		}
 	}
 	return recursive_issubclass(derived, cls);
 }

Objects/enumobject.c

@@ -241,9 +241,12 @@ reversed_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
 				return NULL;
 		}
 	}
-	else
+	else {
 		reversed_meth = _PyObject_LookupSpecial(seq, "__reversed__",
 							&reversed_cache);
+		if (reversed_meth == NULL && PyErr_Occurred())
+			return NULL;
+	}
 	if (reversed_meth != NULL) {
 		PyObject *res = PyObject_CallFunctionObjArgs(reversed_meth, NULL);
 		Py_DECREF(reversed_meth);

Objects/object.c

@@ -509,6 +509,8 @@ PyObject_Unicode(PyObject *v)
 			res = PyObject_CallFunctionObjArgs(func, NULL);
 			Py_DECREF(func);
 		}
+		else if (PyErr_Occurred())
+			return NULL;
 	}
 
 	/* Didn't find __unicode__ */

Python/sysmodule.c

@@ -669,10 +669,12 @@ sys_getsizeof(PyObject *self, PyObject *args, PyObject *kwds)
 	else {
 		PyObject *method = _PyObject_LookupSpecial(o, "__sizeof__",
 							   &str__sizeof__);
-		if (method == NULL)
+		if (method == NULL) {
+			if (!PyErr_Occurred())
 				PyErr_Format(PyExc_TypeError,
 					     "Type %.100s doesn't define __sizeof__",
 					     Py_TYPE(o)->tp_name);
+		}
 		else {
 			res = PyObject_CallFunctionObjArgs(method, NULL);
 			Py_DECREF(method);