From e7d7435ca1fc8e4018b30afd438fd1b5bb2e2b44 Mon Sep 17 00:00:00 2001
From: tonghuaroot <tonghuaroot@gmail.com>
Date: Sat, 11 Jul 2026 11:49:27 +0800
Subject: [PATCH] gh-153537: Fix Element re-init memory leak in the C
 accelerator

element_init allocated a new extra without releasing the previous one,
leaking the element's children and attributes on a second __init__ call.
Clear the old extra first, so re-init discards the previous children and
attributes, matching the pure-Python implementation.
---
 Lib/test/test_xml_etree.py                          | 13 +++++++++++++
 .../2026-07-11-11-36-15.gh-issue-153537.2KySPQ.rst  |  3 +++
 Modules/_elementtree.c                              |  3 +++
 3 files changed, 19 insertions(+)
 create mode 100644 Misc/NEWS.d/next/Library/2026-07-11-11-36-15.gh-issue-153537.2KySPQ.rst

diff --git a/Lib/test/test_xml_etree.py b/Lib/test/test_xml_etree.py
index acec4ec2ca257c4..78ccf4581f7c812 100644
--- a/Lib/test/test_xml_etree.py
+++ b/Lib/test/test_xml_etree.py
@@ -2654,6 +2654,19 @@ def f():
 
 class BasicElementTest(ElementTestCase, unittest.TestCase):
 
+    def test_reinit_releases_children(self):
+        # gh-153537: re-init should release the previous children.
+        e = ET.Element('a', {'k': 'v'})
+        children = [ET.SubElement(e, 'b') for _ in range(3)]
+        refs = [weakref.ref(c) for c in children]
+        del children
+        self.assertEqual(len(e), 3)
+        e.__init__('a')
+        gc_collect()
+        self.assertEqual(len(e), 0)
+        self.assertEqual(e.attrib, {})
+        self.assertTrue(all(ref() is None for ref in refs))
+
     def test___init__(self):
         tag = "foo"
         attrib = { "zix": "wyp" }
diff --git a/Misc/NEWS.d/next/Library/2026-07-11-11-36-15.gh-issue-153537.2KySPQ.rst b/Misc/NEWS.d/next/Library/2026-07-11-11-36-15.gh-issue-153537.2KySPQ.rst
new file mode 100644
index 000000000000000..5fa070be5f7f1c1
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2026-07-11-11-36-15.gh-issue-153537.2KySPQ.rst
@@ -0,0 +1,3 @@
+Re-initializing an :class:`xml.etree.ElementTree.Element` in the C accelerator
+now discards the previous children and attributes instead of leaking them,
+matching the pure-Python implementation. Patch by tonghuaroot.
diff --git a/Modules/_elementtree.c b/Modules/_elementtree.c
index f827274eeffba83..fdd31925604bb29 100644
--- a/Modules/_elementtree.c
+++ b/Modules/_elementtree.c
@@ -449,6 +449,9 @@ element_init(PyObject *self, PyObject *args, PyObject *kwds)
 
     self_elem = (ElementObject *)self;
 
+    /* On re-init, drop any children and attrib from a previous init. */
+    clear_extra(self_elem);
+
     if (attrib != NULL && !is_empty_dict(attrib)) {
         if (create_extra(self_elem, attrib) < 0) {
             Py_DECREF(attrib);