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List:       python-bugs-list
Subject:    [issue6409] 2to3 generates malformed diffs
From:       STINNER Victor <report () bugs ! python ! org>
Date:       2010-01-31 2:05:45
Message-ID: 1264903545.71.0.716613179618.issue6409 () psf ! upfronthosting ! co ! za
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STINNER Victor <victor.stinner@haypocalc.com> added the comment:

I'm able to reproduce the bug. The problem is that "-j 4" option creates 4 working \
processes, and they are all writing to stdout at the same time.

Main process: main() => refactor() => refactor_file() sends tasks to child processes
Children: _child() => queue.get ~> refactor_file() => processed_file() => \
print_output() writes the diff to stdout using print()

A solution would be to use a lock to ensure that only one process is writing to \
stdout at the same time... But we may loose all advantages of using different Python \
processes, it's a new kind of GIL :)

A better solution would be to send output (the whole diff for one file) to the main \
process which will be the only process writing the stdout. I don't know \
multiprocessing enough to propose a patch.

Note: flush() in each child process doesn't ensure that no process is writing to \
stdout at the same time.

----------
nosy: +haypo

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