Issue #19687: Fixed memory leak on failed Element slice assignment.

Added new tests for Element slice assignments.

Lib/test/test_xml_etree.py

@@ -2350,6 +2350,7 @@ class ElementSlicingTest(unittest.TestCase):
         self.assertEqual(e[-2].tag, 'a8')
 
         self.assertRaises(IndexError, lambda: e[12])
+        self.assertRaises(IndexError, lambda: e[-12])
 
     def test_getslice_range(self):
         e = self._make_elem_with_children(6)
@@ -2368,12 +2369,17 @@ class ElementSlicingTest(unittest.TestCase):
         self.assertEqual(self._elem_tags(e[::3]), ['a0', 'a3', 'a6', 'a9'])
         self.assertEqual(self._elem_tags(e[::8]), ['a0', 'a8'])
         self.assertEqual(self._elem_tags(e[1::8]), ['a1', 'a9'])
+        self.assertEqual(self._elem_tags(e[3::sys.maxsize]), ['a3'])
+        self.assertEqual(self._elem_tags(e[3::sys.maxsize<<64]), ['a3'])
 
     def test_getslice_negative_steps(self):
         e = self._make_elem_with_children(4)
 
         self.assertEqual(self._elem_tags(e[::-1]), ['a3', 'a2', 'a1', 'a0'])
         self.assertEqual(self._elem_tags(e[::-2]), ['a3', 'a1'])
+        self.assertEqual(self._elem_tags(e[3::-sys.maxsize]), ['a3'])
+        self.assertEqual(self._elem_tags(e[3::-sys.maxsize-1]), ['a3'])
+        self.assertEqual(self._elem_tags(e[3::-sys.maxsize<<64]), ['a3'])
 
     def test_delslice(self):
         e = self._make_elem_with_children(4)
@@ -2400,6 +2406,75 @@ class ElementSlicingTest(unittest.TestCase):
         del e[::2]
         self.assertEqual(self._subelem_tags(e), ['a1'])
 
+    def test_setslice_single_index(self):
+        e = self._make_elem_with_children(4)
+        e[1] = ET.Element('b')
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b', 'a2', 'a3'])
+
+        e[-2] = ET.Element('c')
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b', 'c', 'a3'])
+
+        with self.assertRaises(IndexError):
+            e[5] = ET.Element('d')
+        with self.assertRaises(IndexError):
+            e[-5] = ET.Element('d')
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b', 'c', 'a3'])
+
+    def test_setslice_range(self):
+        e = self._make_elem_with_children(4)
+        e[1:3] = [ET.Element('b%s' % i) for i in range(2)]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b0', 'b1', 'a3'])
+
+        e = self._make_elem_with_children(4)
+        e[1:3] = [ET.Element('b')]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b', 'a3'])
+
+        e = self._make_elem_with_children(4)
+        e[1:3] = [ET.Element('b%s' % i) for i in range(3)]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b0', 'b1', 'b2', 'a3'])
+
+    def test_setslice_steps(self):
+        e = self._make_elem_with_children(6)
+        e[1:5:2] = [ET.Element('b%s' % i) for i in range(2)]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b0', 'a2', 'b1', 'a4', 'a5'])
+
+        e = self._make_elem_with_children(6)
+        with self.assertRaises(ValueError):
+            e[1:5:2] = [ET.Element('b')]
+        with self.assertRaises(ValueError):
+            e[1:5:2] = [ET.Element('b%s' % i) for i in range(3)]
+        with self.assertRaises(ValueError):
+            e[1:5:2] = []
+        self.assertEqual(self._subelem_tags(e), ['a0', 'a1', 'a2', 'a3', 'a4', 'a5'])
+
+        e = self._make_elem_with_children(4)
+        e[1::sys.maxsize] = [ET.Element('b')]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b', 'a2', 'a3'])
+        e[1::sys.maxsize<<64] = [ET.Element('c')]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'c', 'a2', 'a3'])
+
+    def test_setslice_negative_steps(self):
+        e = self._make_elem_with_children(4)
+        e[2:0:-1] = [ET.Element('b%s' % i) for i in range(2)]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b1', 'b0', 'a3'])
+
+        e = self._make_elem_with_children(4)
+        with self.assertRaises(ValueError):
+            e[2:0:-1] = [ET.Element('b')]
+        with self.assertRaises(ValueError):
+            e[2:0:-1] = [ET.Element('b%s' % i) for i in range(3)]
+        with self.assertRaises(ValueError):
+            e[2:0:-1] = []
+        self.assertEqual(self._subelem_tags(e), ['a0', 'a1', 'a2', 'a3'])
+
+        e = self._make_elem_with_children(4)
+        e[1::-sys.maxsize] = [ET.Element('b')]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'b', 'a2', 'a3'])
+        e[1::-sys.maxsize-1] = [ET.Element('c')]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'c', 'a2', 'a3'])
+        e[1::-sys.maxsize<<64] = [ET.Element('d')]
+        self.assertEqual(self._subelem_tags(e), ['a0', 'd', 'a2', 'a3'])
+
 
 class IOTest(unittest.TestCase):
     def tearDown(self):

Modules/_elementtree.c

@@ -1711,7 +1711,7 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
         Py_ssize_t start, stop, step, slicelen, newlen, cur, i;
 
         PyObject* recycle = NULL;
-        PyObject* seq = NULL;
+        PyObject* seq;
 
         if (!self->extra) {
             if (create_extra(self, NULL) < 0)
@@ -1790,21 +1790,21 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
             Py_XDECREF(recycle);
             return 0;
         }
-        else {
-            /* A new slice is actually being assigned */
-            seq = PySequence_Fast(value, "");
-            if (!seq) {
-                PyErr_Format(
-                    PyExc_TypeError,
-                    "expected sequence, not \"%.200s\"", Py_TYPE(value)->tp_name
-                    );
-                return -1;
-            }
-            newlen = PySequence_Size(seq);
+
+        /* A new slice is actually being assigned */
+        seq = PySequence_Fast(value, "");
+        if (!seq) {
+            PyErr_Format(
+                PyExc_TypeError,
+                "expected sequence, not \"%.200s\"", Py_TYPE(value)->tp_name
+                );
+            return -1;
         }
+        newlen = PySequence_Size(seq);
 
         if (step !=  1 && newlen != slicelen)
         {
+            Py_DECREF(seq);
             PyErr_Format(PyExc_ValueError,
                 "attempt to assign sequence of size %zd "
                 "to extended slice of size %zd",
@@ -1816,9 +1816,7 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
         /* Resize before creating the recycle bin, to prevent refleaks. */
         if (newlen > slicelen) {
             if (element_resize(self, newlen - slicelen) < 0) {
-                if (seq) {
-                    Py_DECREF(seq);
-                }
+                Py_DECREF(seq);
                 return -1;
             }
         }
@@ -1829,9 +1827,7 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
                we're done modifying the element */
             recycle = PyList_New(slicelen);
             if (!recycle) {
-                if (seq) {
-                    Py_DECREF(seq);
-                }
+                Py_DECREF(seq);
                 return -1;
             }
             for (cur = start, i = 0; i < slicelen;
@@ -1859,9 +1855,7 @@ element_ass_subscr(PyObject* self_, PyObject* item, PyObject* value)
 
         self->extra->length += newlen - slicelen;
 
-        if (seq) {
-            Py_DECREF(seq);
-        }
+        Py_DECREF(seq);
 
         /* discard the recycle bin, and everything in it */
         Py_XDECREF(recycle);