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Fix Console.prompt crash on newer Linux kernels (epoll EPERM on /dev/null) - #366
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…null) NIOPipeBootstrap registers the stdin descriptor with epoll_ctl, which returns EPERM for /dev/null on recent kernels, triggering SwiftNIO's 'try!' fatal error. Use readLine() instead of async NIO I/O for prompts. Fixes: xtool auth login < /dev/null crashing with 'epoll_ctl(...): Operation not permitted (errno: 1)'
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The title clearly and concisely describes the main change: preventing a Console.prompt crash caused by epoll EPERM on /dev/null. |
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Reviewed commit: 6dffa040c6
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| return str.hasSuffix("\r") ? String(str.dropLast()) : str | ||
| print(message, terminator: "") | ||
| fflush(stdoutSafe) | ||
| guard let line = readLine() else { |
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On the supported Linux/WSL CLI, when any command is paused here, Ctrl-C no longer exits: XToolCommand.cancellableMain ignores SIGINT and handles it only by calling task.cancel() (Sources/XToolSupport/XTool.swift:77-84), but synchronous readLine() does not observe task cancellation and remains blocked until stdin produces another line or EOF. The parent consequently remains in await task.value, so interactive flows such as auth login stay stuck after the user's interrupt; retain a cancellation-aware read or explicitly unblock this call on cancellation.
AGENTS.md reference: AGENTS.md:L5-L5
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Good catch — addressed in 1f83e66.
The prompt now bridges a blocking FileHandle.read (raw read(), not C stdio) to async via a CheckedContinuation, resumed with CancellationError on cancellation, so SIGINT unblocks and the process exits cleanly.
I deliberately avoided readLine() entirely: besides being non-cancellable, its C stdio lock also deadlocks exit() while a read is blocked.
readLine() is synchronous and doesn't observe task cancellation, so Ctrl-C (SIGINT -> task.cancel() in cancellableMain) left prompts stuck. Bridge the blocking read to async with a CheckedContinuation and run it on a thread, resuming with CancellationError on cancel. Also use FileHandle.read (raw read) instead of readLine(): C stdio holds the stdin lock while blocked, which deadlocks exit() after cancellation.
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Actionable comments posted: 2
- 🪄 Fix comments: Fix CodeRabbit comments on this PR
🤖 Prompt to fix review comments
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Inline comments:
Review comments at @Sources/XToolSupport/Console.swift:
- Around line 19-24: Update PromptRead’s cancellation and continuation handling
so cancellation recorded before install is not lost: store a cancelled state
under the lock, have install immediately resume with CancellationError when that
state is set, and ensure the cancellation path sets it before finishing any
installed continuation.
- Around line 68-70: Update readLineFromStandardInput to propagate errors from
FileHandle.read(upToCount:) instead of treating them as EOF, and carry the
thrown error through the Console.prompt continuation so only actual EOF uses the
existing nil or partial-input result.
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Sources/XToolSupport/Console.swift
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- PromptRead now records cancellation even if it races ahead of install(), so a prompt cancelled before its continuation is installed resumes immediately instead of blocking forever. - readLineFromStandardInput() now throws read errors (instead of swallowing them as EOF); the read thread forwards them through the continuation.
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Problem
xtoolcrashes when an interactive prompt runs with stdin redirected from/dev/null— a common situation in CI and automation:xtool auth login < /dev/nullRoot cause
Console.promptreads stdin through SwiftNIO'sNIOPipeBootstrap(withStdio), which duplicates the stdin descriptor and registers it withepoll_ctl. Recent Linux kernels returnEPERMwhenepoll_ctltargets/dev/null(and other non-epollable character devices). SwiftNIO'stry!inBaseSocketChannel.registerAlreadyConfigured0then turns that into a fatal error.Fix
Replace the NIO pipe bootstrap with the standard library's
readLine(). A CLI prompt doesn't need async I/O — a plain synchronous read is simpler and avoids epoll registration entirely. EOF now surfaces a cleanUnexpected end of input.error instead of trapping.Verification
xtool auth login < /dev/null→Fatal error: epoll_ctl … Operation not permitted(signal 4, exit 132)xtool auth login < /dev/null→Error: Unexpected end of input.(exit 1)printf '0\n' | xtool auth loginstill reads piped input correctlyNotes
NIOPosix/NIOCoreimports fromConsole.swift.chooseNumber/confirmto loop forever).Development
This fix was developed with AI assistance using the DeepSeek model
deepseek-v4-pro(DeepSeek Harness).Summary by CodeRabbit