gh-144503: Pass sys.argv to forkserver as real argv elements#148194
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gpshead merged 1 commit intopython:mainfrom Apr 7, 2026
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gh-144503: Pass sys.argv to forkserver as real argv elements#148194gpshead merged 1 commit intopython:mainfrom
gpshead merged 1 commit intopython:mainfrom
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Avoid embedding the parent's sys.argv into the forkserver -c command string via repr(). When sys.argv is large (e.g. thousands of file paths from a pre-commit hook), the resulting single argument could exceed the OS per-argument length limit (MAX_ARG_STRLEN on Linux, typically 128 KiB), causing posix_spawn to fail and the parent to observe a BrokenPipeError. Instead, append the argv entries as separate command-line arguments after -c; the forkserver child reads them back as sys.argv[1:]. This cannot exceed any limit the parent itself did not already satisfy. Regression introduced by pythongh-143706 / 298d544.
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JelleZijlstra
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Yes, this makes sense and feels safer than the alternative.
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Thanks @gpshead for the PR 🌮🎉.. I'm working now to backport this PR to: 3.13, 3.14. |
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Sorry, @gpshead, I could not cleanly backport this to |
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Sorry, @gpshead, I could not cleanly backport this to |
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…ents (pythonGH-148194) Avoid embedding the parent's sys.argv into the forkserver -c command string via repr(). When sys.argv is large (e.g. thousands of file paths from a pre-commit hook), the resulting single argument could exceed the OS per-argument length limit (MAX_ARG_STRLEN on Linux, typically 128 KiB), causing posix_spawn to fail and the parent to observe a BrokenPipeError. Instead, append the argv entries as separate command-line arguments after -c; the forkserver child reads them back as sys.argv[1:]. This cannot exceed any limit the parent itself did not already satisfy. Regression introduced by pythongh-143706 / 298d544. (cherry picked from commit 5e9d90b) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
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GH-148195 is a backport of this pull request to the 3.14 branch. |
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…ents (pythonGH-148194) Avoid embedding the parent's sys.argv into the forkserver -c command string via repr(). When sys.argv is large (e.g. thousands of file paths from a pre-commit hook), the resulting single argument could exceed the OS per-argument length limit (MAX_ARG_STRLEN on Linux, typically 128 KiB), causing posix_spawn to fail and the parent to observe a BrokenPipeError. Instead, append the argv entries as separate command-line arguments after -c; the forkserver child reads them back as sys.argv[1:]. This cannot exceed any limit the parent itself did not already satisfy. Regression introduced by pythongh-143706 / 298d544. (cherry picked from commit 5e9d90b) Co-authored-by: Gregory P. Smith <68491+gpshead@users.noreply.github.com>
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GH-148196 is a backport of this pull request to the 3.13 branch. |
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…H-148194) (#148195) Avoid embedding the parent's sys.argv into the forkserver -c command string via repr(). When sys.argv is large (e.g. thousands of file paths from a pre-commit hook), the resulting single argument could exceed the OS per-argument length limit (MAX_ARG_STRLEN on Linux, typically 128 KiB), causing posix_spawn to fail and the parent to observe a BrokenPipeError. Instead, append the argv entries as separate command-line arguments after -c; the forkserver child reads them back as sys.argv[1:]. This cannot exceed any limit the parent itself did not already satisfy. Regression introduced by gh-143706 / 298d544. (cherry picked from commit 5e9d90b)
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…H-148194) (#148196) Avoid embedding the parent's sys.argv into the forkserver -c command string via repr(). When sys.argv is large (e.g. thousands of file paths from a pre-commit hook), the resulting single argument could exceed the OS per-argument length limit (MAX_ARG_STRLEN on Linux, typically 128 KiB), causing posix_spawn to fail and the parent to observe a BrokenPipeError. Instead, append the argv entries as separate command-line arguments after -c; the forkserver child reads them back as sys.argv[1:]. This cannot exceed any limit the parent itself did not already satisfy. Regression introduced by gh-143706 / 298d544. (cherry picked from commit 5e9d90b)
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Avoid embedding the parent's sys.argv into the forkserver -c command string via repr(). When sys.argv is large (e.g. thousands of file paths from a pre-commit hook), the resulting single argument could exceed the OS per-argument length limit (MAX_ARG_STRLEN on Linux, typically 128 KiB), causing posix_spawn to fail and the parent to observe a BrokenPipeError.
Instead, append the argv entries as separate command-line arguments after -c; the forkserver child reads them back as sys.argv[1:]. This cannot exceed any limit the parent itself did not already satisfy. (well, almost, we consume two more arguments for the
-c blahso the forkserver only works if there are slightly less than the maximum consumption of command line arguments the platform allows, 2MiB total a.k.a. 1/4 stack size for argv+envp space on Linux in most default configs... a far less common scenario than sys.argv repr'ing to >128KiB)Regression introduced by gh-143706 / 298d544 which landed as a bugfix in 3.14.3 and 3.13.12.
This PR is an alternative to #144508, perhaps less risky to backport as a bugfix.
multiprocessing.Poolfails if command has a long list of arguments (regression in 3.14.3, 3.13.12) #144503