[issue45554] multiprocessing exitcode is insufficiently documented

[Eryk Sun]

Change by Eryk Sun :


--
stage: patch review -> resolved
status: open -> closed

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[issue45554] multiprocessing exitcode is insufficiently documented

[Eryk Sun]

Eryk Sun  added the comment:

PR 30142 is sufficient for Unix, but it's missing a bit for Windows.

In Windows, the C runtime library maps the console event for Ctrl+Break to 
SIGBREAK. The default handler for SIGBREAK exits with 0xC13A (i.e. 
STATUS_CONTROL_C_EXIT). This value is unrelated to the value of signal.SIGBREAK 
(21) or signal.SIGINT (2).

To forcefully terminate a process, Windows taskkill and Task Manager, and 
pretty much all utilities that can kill a process, call TerminateProcess() with 
1 as the exit status. There's no way to know that this is a forced termination 
as opposed to an unhandled error.

The internal terminate() method in Windows uses 0x1 as the real exit status 
of the process, but the internal wait() method maps this to -signal.SIGTERM 
(-15). Thus the case of calling Process.terminate(), and only this case, is 
faked in Windows to look like the process was killed by a signal.

--
nosy: +eryksun
resolution: fixed -> 
stage: resolved -> patch review
status: closed -> open

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[issue45554] multiprocessing exitcode is insufficiently documented

[miss-islington]

miss-islington  added the comment:


New changeset 0be4760d85399a308421d9229b5d7f1b4ec718a2 by Miss Islington (bot) 
in branch '3.9':
[3.9] bpo-45554: Document multiprocessing.Process.exitcode values (GH-30142) 
(GH-30675)
https://github.com/python/cpython/commit/0be4760d85399a308421d9229b5d7f1b4ec718a2


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[issue45554] multiprocessing exitcode is insufficiently documented

[Antoine Pitrou]

Change by Antoine Pitrou :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue45554] multiprocessing exitcode is insufficiently documented

[miss-islington]

miss-islington  added the comment:


New changeset 4449a1694a0fd2c63fcef5eb7d0ad1d7dfbb6077 by Miss Islington (bot) 
in branch '3.10':
bpo-45554: Document multiprocessing.Process.exitcode values (GH-30142)
https://github.com/python/cpython/commit/4449a1694a0fd2c63fcef5eb7d0ad1d7dfbb6077


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[issue45554] multiprocessing exitcode is insufficiently documented

[miss-islington]

Change by miss-islington :


--
pull_requests: +28875
pull_request: https://github.com/python/cpython/pull/30675

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[issue45554] multiprocessing exitcode is insufficiently documented

[miss-islington]

Change by miss-islington :


--
nosy: +miss-islington
nosy_count: 4.0 -> 5.0
pull_requests: +28874
pull_request: https://github.com/python/cpython/pull/30674

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[issue45554] multiprocessing exitcode is insufficiently documented

[miss-islington]

miss-islington  added the comment:


New changeset 3852269b91fcc8ee668cd876b3669eba6da5b1ac by John Marshall in 
branch 'main':
bpo-45554: Document multiprocessing.Process.exitcode values (GH-30142)
https://github.com/python/cpython/commit/3852269b91fcc8ee668cd876b3669eba6da5b1ac


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[issue45554] multiprocessing exitcode is insufficiently documented

[Zachary Ware]

Change by Zachary Ware :


--
nosy: +davin, pitrou
versions: +Python 3.10, Python 3.11, Python 3.9

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[issue45554] multiprocessing exitcode is insufficiently documented

[John Marshall]

John Marshall  added the comment:

Ping -- This issue has an associated PR that expands the 
multiprocessing.Process.exitcode documentation to cover normal, sys.exit(), and 
exception-raised termination of the child process.

https://github.com/python/cpython/pull/30142

The PR has been available for a month but has not received any review comments.

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[issue45554] multiprocessing exitcode is insufficiently documented

[John Marshall]

Change by John Marshall :


--
keywords: +patch
pull_requests: +28360
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/30142

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[issue45554] multiprocessing exitcode is insufficiently documented

[John Marshall]

New submission from John Marshall :


 describes exitcode as

"The child’s exit code. This will be None if the process has not yet 
terminated. A negative value -N indicates that the child was terminated by 
signal N."

and similarly in earlier documentation versions.

This does not describe what the exit code will be under normal circumstances, 
or if the child abends by raising a Python exception.

By examination of BaseProcess._bootstrap() it can be determined that the 
current behaviour appears to be:

* even if your subclass overrides the run() method, whatever this method 
returns is ignored (and in particular the return value has no effect on the 
child's exit code);

* if the run() method returns normally, the child's exit code will be 0;

* if the run() method raises SystemExit (or, I guess, calls sys.exit()) with an 
integer exit status, that exit status will be propagated to the child's exit 
code;

* if the run() method raises any other exception, the exception traceback will 
be printed to stderr and the child's exit code will be 1.


However I did not see a way to figure these details out from the documentation, 
and it is unclear whether all these details are supported behaviours.

--
assignee: docs@python
components: Documentation
messages: 404597
nosy: docs@python, jmarshall
priority: normal
severity: normal
status: open
title: multiprocessing exitcode is insufficiently documented
type: behavior

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