Pipe inheritance broken on Windows since 3.13

Bug report

Bug description:

Passing an inheritable pipe file descriptor to a child process is somehow broken on Windows since Python 3.13. Opening the file descriptor in the child process crashes with [WinError 6] the handle is invalid.

> py -3.12-64 .\main.py
INFO:root:S: Starting
INFO:root:Duration for 10000 requests: 0.37447249999968335 s
INFO:root:S: EOF Quitting
> py -3.13-64 .\main.py
INFO:root:S: Starting
Traceback (most recent call last):
  File "D:\temp\test-pipe-main\sub.py", line 31, in <module>
    main()
    ~~~~^^
  File "D:\temp\test-pipe-main\sub.py", line 14, in main
    reply_write_fobj = os.fdopen(reply_write_fd, "wb", buffering=0)
  File "<frozen os>", line 1068, in fdopen
OSError: [WinError 6] Das Handle ist ungültig

Minimal example

import logging
import os
import pickle
import sys
import time


def main():
    logging.basicConfig(level=logging.INFO)
    reply_read_fd, reply_write_fd = os.pipe()
    request_read_fd, request_write_fd = os.pipe()
    child_fds = [reply_write_fd, request_read_fd]
    for fd in child_fds:
        os.set_inheritable(fd, True)

    reply_read_fobj = os.fdopen(reply_read_fd, "rb", buffering=0)
    request_write_fobj = os.fdopen(request_write_fd, "wb", buffering=0)

    child_pid = os.spawnl(
        os.P_NOWAIT,
        sys.executable,
        os.path.basename(sys.executable),
        "sub.py",
        *(str(fd) for fd in child_fds),
    )
    for fd in child_fds:
        os.close(fd)

    number_requests = 10000
    start = time.perf_counter()
    for i in range(number_requests):
        request = f"test{i}"
        pickle.dump(request, request_write_fobj)
        logging.debug(f"C: Sent {request}")
        reply = pickle.load(reply_read_fobj)
        logging.debug(f"C: Got {reply}")

    duration = time.perf_counter() - start
    logging.info(f"Duration for {number_requests} requests: {duration} s")
    request_write_fobj.close()
    os.waitpid(child_pid, 0)
    time.sleep(1)


if __name__ == "__main__":
    main()

import logging
import os
import pickle
import sys


def main():
    logging.basicConfig(level=logging.INFO)
    reply_write_fd = int(sys.argv[1])
    request_read_fd = int(sys.argv[2])

    logging.info("S: Starting")

    reply_write_fobj = os.fdopen(reply_write_fd, "wb", buffering=0)
    request_read_fobj = os.fdopen(request_read_fd, "rb", buffering=0)
    logging.debug("S: Sent event")
    while True:
        try:
            request: str = pickle.load(request_read_fobj)
        except EOFError:
            logging.info("S: EOF Quitting")
            return
        logging.debug(f"S: Handle {request}")
        reply = "test"
        pickle.dump(reply, reply_write_fobj)

        logging.debug("S: Sent event")


if __name__ == "__main__":
    main()

CPython versions tested on:

3.12, 3.13

Operating systems tested on:

Windows

Bắt đầu bằng cách chạy main.py và sub.py được cung cấp trên Windows với Python 3.12 và 3.13, tập trung vào os.pipe, os.set_inheritable, os.spawnl và os.fdopen. Theo dõi đường đi của tiến trình Windows và quá trình kế thừa pipe để xác định lý do tiến trình con nhận được một handle không hợp lệ, sau đó xác minh bản sửa bằng một bài kiểm thử hồi quy bao quát ví dụ tối thiểu.