gh-143249: Fix buffer leak when overlapped operation fails to start (OS-Windows)

[hyongtao-code]

On Windows, some overlapped I/O operations leak buffers when they fail to start, notably in WSASendTo(), WSARecvFrom(), and WSARecvFromInto().

This change ensures that buffers are released on failure by clearing the overlapped state, following the same pattern used in other overlapped error paths. This issue is similar in nature to commit 5485085, which fixed related overlapped cleanup problems.

Python script for tracking leaks

import sys
import _overlapped

def total():
    return sys.gettotalrefcount()

if not hasattr(sys, "gettotalrefcount"):
    raise SystemExit("need a debug build (Py_DEBUG) for gettotalrefcount")

before = total()

N = 20000
STEP = 1000

for i in range(1, N + 1):
    ov = _overlapped.Overlapped()
    buf = memoryview(bytearray(4096))
    try:
        ov.WSASendTo(0x1234, buf, 0, ("127.0.0.1", 1))
    except OSError:
        pass

    if i % STEP == 0:
        now = total()
        print(f"{i:6d}: totalrefcount delta = {now - before:+d}")

after = total()
print(f"done: N={N}, totalrefcount delta = {after - before:+d}")

Result without the patch

d:\MyCode\cpython\PCbuild\amd64>python_d.exe py_overlapped_leak.py
  1000: totalrefcount delta = +4007
  2000: totalrefcount delta = +8009
  3000: totalrefcount delta = +11906
  4000: totalrefcount delta = +15906
  5000: totalrefcount delta = +19906
......
 19000: totalrefcount delta = +75906
 20000: totalrefcount delta = +79906
done: N=20000, totalrefcount delta = +79905

Result with the patch

d:\MyCode\cpython\PCbuild\amd64>python_d.exe py_overlapped_leak.py
  1000: totalrefcount delta = +10
  2000: totalrefcount delta = +10
  3000: totalrefcount delta = +10
  4000: totalrefcount delta = +10
  5000: totalrefcount delta = +10
......
 19000: totalrefcount delta = +10
 20000: totalrefcount delta = +10
done: N=20000, totalrefcount delta = +9

• Issue: Overlapped I/O leaks buffers when operation fails to start #143249

[picnixz]

You'll need a NEWS entry for that and some tests as well. Please add them so that we can run them under the refleak bot as well.

cc @zooba

wrong button

[hyongtao-code]

and some tests as well

Thanks for the review. I will add a suitable test case.

[serhiy-storchaka]

LGTM. 👍

[miss-islington-app]

Thanks @hyongtao-code for the PR, and @kumaraditya303 for merging it 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14.
🐍🍒⛏🤖

[bedevere-app]

GH-143795 is a backport of this pull request to the 3.14 branch.

[bedevere-app]

GH-143796 is a backport of this pull request to the 3.13 branch.