Memory leak when re-initializing an Element in the _elementtree C accelerator

[tonghuaroot]

Bug report

Bug description:

The _elementtree C accelerator's Element.__init__ (element_init) calls create_extra, which allocates a new extra without freeing the previous one. Re-initializing an element that already has children or attributes therefore leaks them; the pure-Python Element.__init__ resets the children, so the two implementations diverge.

Repro (prints three live Elements on the C accelerator, [None, None, None] on pure Python):

import gc, weakref
from _elementtree import Element, SubElement
e = Element('a')
kids = [SubElement(e, 'b') for _ in range(3)]
refs = [weakref.ref(k) for k in kids]
del kids
Element.__init__(e, 'a')
gc.collect()
print([r() for r in refs])

Fix: clear the existing extra at the start of element_init (the file already has clear_extra), matching the pure-Python reset.

CPython versions tested on:

3.13, 3.14, CPython main branch

Operating systems tested on:

macOS

Linked PRs

• gh-153537: Fix Element re-init memory leak in the C accelerator #153538