Description

assignee = None
closed_at = <Date 2018-03-11.19:10:52.978>
created_at = <Date 2017-10-17.14:59:34.932>
labels = ['3.7', '3.8', 'type-bug', 'library']
title = 'multiprocessing calls flush on sys.stdout at exit even if it is None (pythonw)'
updated_at = <Date 2018-03-11.19:10:52.977>
user = 'https://github.com/poxthegreat'

activity = <Date 2018-03-11.19:10:52.977>
actor = 'pitrou'
assignee = 'none'
closed = True
closed_date = <Date 2018-03-11.19:10:52.978>
closer = 'pitrou'
components = ['Library (Lib)']
creation = <Date 2017-10-17.14:59:34.932>
creator = 'Pox TheGreat'
dependencies = []
files = ['47224']
hgrepos = []
issue_num = 31804
keywords = ['patch']
message_count = 12.0
messages = ['304512', '304678', '309708', '309716', '309721', '309759', '309762', '309853', '313608', '313613', '313616', '313617']
nosy_count = 4.0
nosy_names = ['terry.reedy', 'pitrou', 'davin', 'Pox TheGreat']
pr_nums = ['5492', '6079', '6080', '6081']
priority = 'normal'
resolution = 'fixed'
stage = 'resolved'
status = 'closed'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue31804'
versions = ['Python 3.6', 'Python 3.7', 'Python 3.8']

Activity

1. poxthegreat commented on Oct 17, 2017

   

   poxthegreatmannequin

   on Oct 17, 2017

   MannequinAuthor

   More actions

   If you start Python by pythonw then sys.stdout and sys.stderr are set to None. If you also use multiprocessing then when the child process finishes BaseProcess._bootstrap calls sys.stdout.flush() and sys.stderr.flush() finally. This causes the process return code to be not zero (it is 1).
2. poxthegreat

   added

   type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

   stdlibStandard Library Python modules in the Lib/ directoryStandard Library Python modules in the Lib/ directory

   on Oct 17, 2017
3. terryjreedy

   added

   3.7 (EOL)end of lifeend of life

   on Oct 20, 2017
4. pitrou commented on Oct 20, 2017

   

   pitrou

   on Oct 20, 2017

   Member

   More actions

   This looks to be a duplicate of https://bugs.python.org/issue28326
5. pitrou

   closed this as completedon Oct 20, 2017
6. poxthegreat commented on Jan 9, 2018

   

   poxthegreatmannequin

   on Jan 9, 2018

   MannequinAuthor

   More actions

   Unfortunately this is NOT a duplicate of https://bugs.python.org/issue28326. That issue is about a closed output stream. In that case sys.stdout and sys.stderr are file like objects which have been closed.

   This issue is about sys.stdout and sys.stderr being None! This is because pythonw was used not python.
7. poxthegreat

   reopened this on Jan 9, 2018
8. pitrou commented on Jan 9, 2018

   

   pitrou

   on Jan 9, 2018

   Member

   More actions

   @pox, nevertheless, the fix committed in #4073 should also fix this issue. Do you disagree?
9. terryjreedy commented on Jan 9, 2018

   

   terryjreedy

   on Jan 9, 2018

   Member

   More actions

   Pox, please retest with either 3.6.4 or 3.7.0a3 (or .0a4 when released, soon). Both were released after the merge that should fix this.
10. poxthegreat commented on Jan 10, 2018

    

    poxthegreatmannequin

    on Jan 10, 2018

    MannequinAuthor

    More actions

    Retested it with a freshly installed 3.6.4 version. Used the following code to test:

    import sys
    import multiprocessing
    
    
    def foo():
        return 'bar'
    
    
    if __name__ == '__main__':
        proc = multiprocessing.Process(target=foo)
        proc.start()
        proc.join()
        with open('process_exit_code.txt', 'w') as f:
            f.write(sys.version)
            f.write('\nprocess exit code: ')
            f.write(str(proc.exitcode))

    It is very important to run the script with pythonw, not just with python. This is the content of the resulting process_exit_code.txt file on my machine:
    3.6.4 (v3.6.4:d48eceb, Dec 19 2017, 06:04:45) [MSC v.1900 32 bit (Intel)]
    process exit code: 1

    As it can be seen the problem was not fixed. The process exit code should be 0. By default the new multiprocessing process created uses the same interpreter as the creator process, so it uses pythonw too.
11. pitrou commented on Jan 10, 2018

    

    pitrou

    on Jan 10, 2018

    Member

    More actions

    I'm not using Windows, so I'm unable to test using pythonw. You'll have to provide a fix, or someone else will have to.
12. poxthegreat commented on Jan 12, 2018

    

    poxthegreatmannequin

    on Jan 12, 2018

    MannequinAuthor

    More actions

    I have already uploaded a patch file but it is not in the required format. Also I realize that most of the confusion was because I forgot to provide the OS version. Perhaps it would be good to have a separate field for that.

    I will upload a patch as it is described in the developer guide.
13. poxthegreat

    added

    type-bugAn unexpected behavior, bug, or errorAn unexpected behavior, bug, or error

    and removed

    type-crashA hard crash of the interpreter, possibly with a core dumpA hard crash of the interpreter, possibly with a core dump

    on Jan 12, 2018
14. pitrou commented on Mar 11, 2018

    

    pitrou

    on Mar 11, 2018

    Member

    More actions

    New changeset e756f66 by Antoine Pitrou in branch 'master':
    bpo-31804: Fix multiprocessing.Process with broken standard streams (bpo-6079)
    e756f66
15. pitrou

    added

    3.8 (EOL)end of lifeend of life

    on Mar 11, 2018
16. pitrou commented on Mar 11, 2018

    

    pitrou

    on Mar 11, 2018

    Member

    More actions

    New changeset ff5d213 by Antoine Pitrou (Miss Islington (bot)) in branch '3.7':
    bpo-31804: Fix multiprocessing.Process with broken standard streams (GH-6079) (GH-6080)
    ff5d213
17. pitrou commented on Mar 11, 2018

    

    pitrou

    on Mar 11, 2018

    Member

    More actions

    New changeset 069b8d2 by Antoine Pitrou in branch '3.6':
    [3.6] bpo-31804: Fix multiprocessing.Process with broken standard streams (GH-6079) (GH-6081)
    069b8d2
18. pitrou commented on Mar 11, 2018

    

    pitrou

    on Mar 11, 2018

    Member

    More actions

    This is all fixed in the Python 3 branches now. I won't bother with Python 2 as it has quite a different code structure and backporting would take too much of my time.

    Pox TheGreat, thanks for reporting and the initial patch!
19. pitrou

    closed this as completedon Mar 11, 2018
20. ezio-melotti

    transferred this issue fromon Apr 10, 2022

Issue actions