gh-135335: flush stdout/stderr in forkserver after preloadi 8000 ng modules #135338
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…odules If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload.
...or at least produce more useful output if they fail
efimov-mikhail
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Jun 11, 2025
… if the defaults change elsewhere in the future)
vstinner
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Jun 17, 2025
…use a not-completely-awful name for the module to test.
Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com>
vstinner
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vstinner
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vstinner
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Co-authored-by: Victor Stinner <vstinner@python.org>
vstinner
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Jun 17, 2025
Misc/NEWS.d/next/Library/2025-06-10-21-42-04.gh-issue-135335.WnUqb_.rst
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Co-authored-by: Victor Stinner <vstinner@python.org>
…nUqb_.rst Co-authored-by: Victor Stinner <vstinner@python.org>
vstinner
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Jun 18, 2025
miss-islington
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…odules (pythonGH-135338) If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload. (cherry picked from commit 9877d19) Co-authored-by: Duane Griffin <duaneg@dghda.com> Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com> Co-authored-by: Victor Stinner <vstinner@python.org>
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GH-135670 is a backport of this pull request to the 3.14 branch. |
miss-islington
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…odules (pythonGH-135338) If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload. (cherry picked from commit 9877d19) Co-authored-by: Duane Griffin <duaneg@dghda.com> Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com> Co-authored-by: Victor Stinner <vstinner@python.org>
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GH-135671 is a backport of this pull request to the 3.13 branch. |
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Thanks for the bug report and the fix @duaneg. |
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Thanks for the reviews, folks. |
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…modules (GH-135338) (#135671) gh-135335: flush stdout/stderr in forkserver after preloading modules (GH-135338) If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload. (cherry picked from commit 9877d19) Co-authored-by: Duane Griffin <duaneg@dghda.com> Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com> Co-authored-by: Victor Stinner <vstinner@python.org>
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…modules (GH-135338) (#135670) gh-135335: flush stdout/stderr in forkserver after preloading modules (GH-135338) If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload. (cherry picked from commit 9877d19) Co-authored-by: Duane Griffin <duaneg@dghda.com> Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com> Co-authored-by: Victor Stinner <vstinner@python.org>
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Thanks for thorough working on this PR! |
Well, as it happens, I would love #132574 to get a review 🙂 It is a very simple bug and fix: an off-by-one error, that allows an out-of-bounds read, which affects basic string operations like |
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Ok, I'll take a look. |
lkollar
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Jun 19, 2025
…odules (python#135338) If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload. Co-authored-by: Mikhail Efimov <efimov.mikhail@gmail.com> Co-authored-by: Victor Stinner <vstinner@python.org>
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If a preloaded module writes to stdout or stderr, and the stream is buffered, child processes will inherit the buffered data after forking. Attempt to prevent this by flushing the streams after preload.