select: validate and expand Windows descriptor capacity by youknowdot · Pull Request #9021 · RustPython/RustPython

youknowdot · 2026-10-09T12:29:51Z

Scope

Match Python 3.14's Windows select.select() capacity of 512 entries. RustPython currently uses the Windows SDK default of 64.

This draft deliberately starts with a regression-only commit. Its Windows RustPython snippet is expected to fail on the current baseline; that failure will establish native-platform evidence before the implementation is added to the same draft branch. The existing workflow runs the CPython reference and RustPython on Windows. The implementation and subsequent verification will remain in this PR's commit history and checks.

Regression

Ordinary local socket pairs, with no external network service.
Successful readiness selection for 65 entries on all supported hosts.
Successful readiness selection for 512 entries on Windows.
Windows rejection of a 513-entry input remains required.
Existing select regression assertions stay unchanged.

Evidence at draft creation

CPython 3.14 explicitly defines Windows FD_SETSIZE as 512: selectmodule.c.
The focused snippet passes through the repository's pytest runner on CPython 3.14.7 and the current Linux RustPython baseline.
The existing Windows CI environment has already run this snippet's 4096-socket setup successfully on both interpreters. The new capacity assertions still require their own Windows result.
Normal repository commit hooks pass.

This is a Python 3.14 compatibility extraction from #8954. No Python 3.15 API or test-expectation changes are included.

AI assistance: OpenAI Codex assisted with source comparison, regression design, implementation preparation, and automated verification under the user's direction. No manual Windows validation is claimed.

Add local-socket readiness coverage for 65 entries and the Windows 512-entry limit, preserving 513-entry rejection. This regression-only commit intentionally leaves the current Windows 64-entry defect visible before the implementation is added. AI assistance covered regression design, CPython 3.14 source comparison, and automated Linux baseline/reference testing. No manual Windows validation is claimed. Assisted-by: Codex:model-version-unavailable

coderabbitai · 2026-10-09T12:30:00Z

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crates/host_env/src/select.rs
extra_tests/snippets/stdlib_select.py

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codspeed · 2026-10-09T12:51:19Z

Merging this PR will not alter performance

✅ 62 untouched benchmarks
⏩ 4 skipped benchmarks¹

_{Comparing youknowdot:fix-windows-select-capacity (4de6987) with main (bd8fdb7)}

4 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

Use a 512-entry WinSock fd_set with checked C layout and scan its returned socket array. Keep the SDK default-size declaration at the FFI boundary only. The preceding regression-only commit passed CPython 3.14.7 on hosted Windows and failed RustPython at the first 65-socket selection. Windows-GNU host_env cargo check and Clippy with warnings denied pass. The fixed native Windows runtime result remains pending CI. AI assistance covered source comparison, implementation, regression design, and automated verification. No manual validation is claimed. Assisted-by: Codex:model-version-unavailable

chatgpt-codex-connector · 2026-10-09T14:26:08Z

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Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-09T14:30:30.420035Z	`bca89e6`	Draft marked ready

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chatgpt-codex-connector · 2026-10-09T14:30:27Z



+# Windows supports up to 512 entries, above the Windows SDK default of 64.
+for count in (65, 512) if sys.platform == "win32" else (65,):


Remove the disallowed test-file changes

This newly added loop introduces test data, control flow, and assertions in a test file, but the root AGENTS.md limits test-file modifications to adding or removing expected-failure markers. Remove this regression block from the test file (or update the repository policy before landing it).

AGENTS.md reference: AGENTS.md:L275-L279

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youknowone approved these changes Oct 9, 2026

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youknowone marked this pull request as ready for review October 9, 2026 14:25

youknowone merged commit fe984ce into RustPython:main Oct 9, 2026
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chatgpt-codex-connector Bot reviewed Oct 9, 2026

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select: validate and expand Windows descriptor capacity - #9021

select: validate and expand Windows descriptor capacity#9021
youknowone merged 2 commits into
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youknowdot:fix-windows-select-capacity

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		# Windows supports up to 512 entries, above the Windows SDK default of 64.
		for count in (65, 512) if sys.platform == "win32" else (65,):

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youknowdot commented Oct 9, 2026

Scope

Regression

Evidence at draft creation

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codspeed Bot commented Oct 9, 2026

Merging this PR will not alter performance

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