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GH-109190: Copyedit 3.12 What's New: Deprecations (os fix) #109927

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Sep 27, 2023
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GH-109190: Copyedit 3.12 What's New: Deprecations (os fix) #109927

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32 changes: 17 additions & 15 deletions Doc/whatsnew/3.12.rst
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Expand Up @@ -1114,12 +1114,6 @@ Deprecated
volume and maintenance burden.
(Contributed by Raymond Hettinger in :gh:`101588`.)

* :mod:`os`: The ``st_ctime`` fields return by :func:`os.stat` and :func:`os.lstat` on
Windows are deprecated. In a future release, they will contain the last
metadata change time, consistent with other platforms. For now, they still
contain the creation time, which is also available in the new ``st_birthtime``
field. (Contributed by Steve Dower in :gh:`99726`.)

* :mod:`multiprocessing`: In Python 3.14, the default :mod:`multiprocessing`
start method will change to a safer one on Linux, BSDs,
and other non-macOS POSIX platforms where ``'fork'`` is currently
Expand All @@ -1140,15 +1134,23 @@ Deprecated
proper :exc:`DeprecationWarning` in 3.12. Remove them in 3.14.
(Contributed by Soumendra Ganguly and Gregory P. Smith in :gh:`85984`.)

* :mod:`os`: On POSIX platforms, :func:`os.fork` can now raise a
:exc:`DeprecationWarning` when it can detect being called from a
multithreaded process. There has always been a fundamental incompatibility
with the POSIX platform when doing so. Even if such code *appeared* to work.
We added the warning to to raise awareness as issues encounted by code doing
this are becoming more frequent. See the :func:`os.fork` documentation for
more details along with `this discussion on fork being incompatible with threads
<https://discuss.python.org/t/33555>`_ for *why* we're now surfacing this
longstanding platform compatibility problem to developers.
* :mod:`os`:

* The ``st_ctime`` fields return by :func:`os.stat` and :func:`os.lstat` on
Windows are deprecated. In a future release, they will contain the last
metadata change time, consistent with other platforms. For now, they still
contain the creation time, which is also available in the new ``st_birthtime``
field. (Contributed by Steve Dower in :gh:`99726`.)

* On POSIX platforms, :func:`os.fork` can now raise a
:exc:`DeprecationWarning` when it can detect being called from a
multithreaded process. There has always been a fundamental incompatibility
with the POSIX platform when doing so. Even if such code *appeared* to work.
We added the warning to to raise awareness as issues encounted by code doing
this are becoming more frequent. See the :func:`os.fork` documentation for
more details along with `this discussion on fork being incompatible with threads
<https://discuss.python.org/t/33555>`_ for *why* we're now surfacing this
longstanding platform compatibility problem to developers.

When this warning appears due to usage of :mod:`multiprocessing` or
:mod:`concurrent.futures` the fix is to use a different
Expand Down