From b6aa5375d5a2f81370338357506034befe62aa31 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Mon, 23 Nov 2015 08:42:25 +0200
Subject: Issue #25691: Fixed crash on deleting ElementTree.Element attributes.

---
 Lib/test/test_xml_etree.py   | 27 +++++++++++++++++++++++++++
 Lib/test/test_xml_etree_c.py | 32 ++++++++++++++++++++++++++++++++
 Misc/NEWS                    |  2 ++
 Modules/_elementtree.c       |  6 ++++++
 4 files changed, 67 insertions(+)

diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index 9261592..8511cfe 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -244,6 +244,33 @@ class ElementTreeTest(unittest.TestCase):
         self.assertEqual(ET.XML, ET.fromstring)
         self.assertEqual(ET.PI, ET.ProcessingInstruction)
 
+    def test_set_attribute(self):
+        element = ET.Element('tag')
+
+        self.assertEqual(element.tag, 'tag')
+        element.tag = 'Tag'
+        self.assertEqual(element.tag, 'Tag')
+        element.tag = 'TAG'
+        self.assertEqual(element.tag, 'TAG')
+
+        self.assertIsNone(element.text)
+        element.text = 'Text'
+        self.assertEqual(element.text, 'Text')
+        element.text = 'TEXT'
+        self.assertEqual(element.text, 'TEXT')
+
+        self.assertIsNone(element.tail)
+        element.tail = 'Tail'
+        self.assertEqual(element.tail, 'Tail')
+        element.tail = 'TAIL'
+        self.assertEqual(element.tail, 'TAIL')
+
+        self.assertEqual(element.attrib, {})
+        element.attrib = {'a': 'b', 'c': 'd'}
+        self.assertEqual(element.attrib, {'a': 'b', 'c': 'd'})
+        element.attrib = {'A': 'B', 'C': 'D'}
+        self.assertEqual(element.attrib, {'A': 'B', 'C': 'D'})
+
     def test_simpleops(self):
         # Basic method sanity checks.
 
diff --git a/Lib/test/test_xml_etree_c.py b/Lib/test/test_xml_etree_c.py
index 816aa86..409ec6a 100644
--- a/Lib/test/test_xml_etree_c.py
+++ b/Lib/test/test_xml_etree_c.py
@@ -22,6 +22,38 @@ class MiscTests(unittest.TestCase):
         finally:
             data = None
 
+    def test_del_attribute(self):
+        element = cET.Element('tag')
+
+        element.tag = 'TAG'
+        with self.assertRaises(AttributeError):
+            del element.tag
+        self.assertEqual(element.tag, 'TAG')
+
+        with self.assertRaises(AttributeError):
+            del element.text
+        self.assertIsNone(element.text)
+        element.text = 'TEXT'
+        with self.assertRaises(AttributeError):
+            del element.text
+        self.assertEqual(element.text, 'TEXT')
+
+        with self.assertRaises(AttributeError):
+            del element.tail
+        self.assertIsNone(element.tail)
+        element.tail = 'TAIL'
+        with self.assertRaises(AttributeError):
+            del element.tail
+        self.assertEqual(element.tail, 'TAIL')
+
+        with self.assertRaises(AttributeError):
+            del element.attrib
+        self.assertEqual(element.attrib, {})
+        element.attrib = {'A': 'B', 'C': 'D'}
+        with self.assertRaises(AttributeError):
+            del element.attrib
+        self.assertEqual(element.attrib, {'A': 'B', 'C': 'D'})
+
 
 @unittest.skipUnless(cET, 'requires _elementtree')
 class TestAliasWorking(unittest.TestCase):
diff --git a/Misc/NEWS b/Misc/NEWS
index a13e198..635da46 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -106,6 +106,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #25691: Fixed crash on deleting ElementTree.Element attributes.
+
 - Issue #25624: ZipFile now always writes a ZIP_STORED header for directory
   entries.  Patch by Dingyuan Wang.
 
diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index da784a0..3b6ee89 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -1852,6 +1852,12 @@ static int
 element_setattro(ElementObject* self, PyObject* nameobj, PyObject* value)
 {
     char *name = "";
+
+    if (value == NULL) {
+        PyErr_SetString(PyExc_AttributeError,
+            "can't delete attribute");
+        return -1;
+    }
     if (PyUnicode_Check(nameobj))
         name = _PyUnicode_AsString(nameobj);
     if (name == NULL)
-- 
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