gh-135335: flush stdout/stderr in forkserver after preloading modules #135338
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…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
suggested changes
Jun 11, 2025
… if the defaults change elsewhere in the future)
vstinner
reviewed
Jun 17, 2025
…use a not-completely-awful name for the module to test.
Co-authored-by: Mikhail Efimov <[email protected]>
vstinner
reviewed
Jun 17, 2025
vstinner
reviewed
Jun 17, 2025
vstinner
reviewed
Jun 17, 2025
Co-authored-by: Victor Stinner <[email protected]>
vstinner
reviewed
Jun 17, 2025
Misc/NEWS.d/next/Library/2025-06-10-21-42-04.gh-issue-135335.WnUqb_.rst
Outdated
Show resolved
Hide resolved
Co-authored-by: Victor Stinner <[email protected]>
…nUqb_.rst Co-authored-by: Victor Stinner <[email protected]>
vstinner
approved these changes
Jun 18, 2025
vstinner
added
needs backport to 3.13
miss-islington
pushed a commit
to miss-islington/cpython
that referenced
this pull request
Jun 18, 2025
…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 <[email protected]> Co-authored-by: Mikhail Efimov <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
|
GH-135670 is a backport of this pull request to the 3.14 branch. |
miss-islington
pushed a commit
to miss-islington/cpython
that referenced
this pull request
Jun 18, 2025
…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 <[email protected]> Co-authored-by: Mikhail Efimov <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
|
GH-135671 is a backport of this pull request to the 3.13 branch. |
|
Thanks for the bug report and the fix @duaneg. |
|
Thanks for the reviews, folks. |
vstinner
added a commit
that referenced
this pull request
Jun 18, 2025
…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 <[email protected]> Co-authored-by: Mikhail Efimov <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
vstinner
added a commit
that referenced
this pull request
Jun 18, 2025
…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 <[email protected]> Co-authored-by: Mikhail Efimov <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
|
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 |
|
Ok, I'll take a look. |
lkollar
pushed a commit
to lkollar/cpython
that referenced
this pull request
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 <[email protected]> Co-authored-by: Victor Stinner <[email protected]>
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
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.