[codex] Fix libxev poller state leaks#432
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The drain loop in run_xev_close_fd waited only for the original read/write
completions to retire, ignoring the cancel completions we submitted to
libxev. When the cancel CQE was still pending in the io_uring ring, the
function would zero slot.read_cancel = .{}, setting its op to .noop. When
the kernel eventually delivered that CQE, libxev's Completion.invoke()
hit `.noop => unreachable`, crashing with SIGSEGV in
test_poller_close_while_waiting.
Three layered fixes:
1. run_xev_bridge.zig: Drain loop now also waits for read_cancel and
write_cancel completions to reach .dead before resetting their
storage. Reset is now conditional: any completion that is somehow
still .active (drain exhausted) is left alone so its eventual CQE
finds a valid op.
2. libxev io_uring.zig: Mirror the existing kqueue.zig defensive guard —
skip processing CQEs for completions whose flags.state is no longer
.active. This prevents the unreachable crash even if a future caller
resets a completion mid-flight.
3. libxev io_uring.zig: Handle .CANCELED in the .poll case so the
cancelled poll's CQE no longer prints "unexpected errno: 125" to
stderr.
https://claude.ai/code/session_01CSYWLMHrkzjcwCbEwHtCLT
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Summary
Issues
Fixes #397
Fixes #416
Fixes #424
Fixes #426
Audited #395 and #396: the libxev adapter and default poller wiring are already present on origin/main; this PR fixes the remaining state leak/test gating around that implementation.
Validation
zig buildzig build test(passes; emits the expected negative-test diagnostic formissing())zig build test-runtimezig build test-runtime -Dsanitize=truecould not run on this macOS host becauselibasanandlibubsanare not available in the SDK/Homebrew library paths.