Windows os.stat and os.fstat report different st_ctime_ns values

Python/fileutils.c の _Py_attribute_data_to_stat と _Py_fstat_noraise から始め、次に Modules/posixmodule.c の os_fstat_impl と win32_xstat を調べます。Windows で提供された再現手順を実行し、os.stat() と os.fstat() が一致する ctime_ns 値を報告すると同時に、示されている作成時刻の動作が維持されることを確認します。

Bug description:

On Windows, os.stat(path).st_ctime_ns and os.fstat(fd).st_ctime_ns can differ for the same file.

I ran the example below on Windows 11 with NTFS. It fails with both official Python 3.14.7 Windows builds: ARM64 running natively and x64 running under emulation. The same-file assertion passes, but the timestamp assertion fails. Both st_birthtime_ns values equal os.stat(path).st_ctime_ns.

In the 3.14.7 code:

• _Py_attribute_data_to_stat assigns FILE_BASIC_INFO.ChangeTime to st_ctime.
• _Py_fstat_noraise returns that result. os_fstat_impl does not change the timestamp.
• win32_xstat replaces st_ctime and its nanoseconds with st_birthtime for compatibility.

Commit a01fb672 added that compatibility step. The discussion in #102149 says st_ctime should continue returning creation time during the deprecation period. Should fstat() do the same?

In #117354, DirEntry.stat() was changed to return creation time during the same deprecation period, following #117267.

Example:

import os
import time
from pathlib import Path
from tempfile import TemporaryDirectory

with TemporaryDirectory() as directory:
    path = Path(directory) / "example.txt"
    path.write_text("before")
    time.sleep(0.1)
    path.write_text("after")

    with path.open("rb") as source:
        by_path = os.stat(path)
        by_fd = os.fstat(source.fileno())

    print("stat ctime:", by_path.st_ctime_ns)
    print("fstat ctime:", by_fd.st_ctime_ns)
    print("stat birthtime:", getattr(by_path, "st_birthtime_ns", None))
    print("fstat birthtime:", getattr(by_fd, "st_birthtime_ns", None))
    assert os.path.samestat(by_path, by_fd)
    assert by_path.st_ctime_ns == by_fd.st_ctime_ns

Output from the official Python 3.14.7 ARM64 build:

stat ctime: 1789643317486473600
fstat ctime: 1789643317591142500
stat birthtime: 1789643317486473600
fstat birthtime: 1789643317486473600

The final assertion raises AssertionError.

CPython versions tested on:

• 3.10.20 (conda-forge build): timestamps match.
• 3.14.6 (Anaconda build): timestamps differ.
• 3.14.7: timestamps differ with both official Windows embeddable builds, ARM64 and x64.

Operating systems tested on:

Windows 11 ARM64, build 26200.9457, in Parallels Desktop. The test files were on NTFS. The ARM64 Python build ran natively and the x64 build ran under Windows emulation.