fix(cmplog): stop() closes the FIFO drain

[daedalus]

Follow-up to #26 review.

• Sourcery (bug_risk), confirmed in production: CmplogCollector.stop() unlinked the FIFO but never called _FifoDrain.close(), so the drain thread kept polling and both FIFO fds stayed open. FIFO sink is the CLI default, so every run leaked this. stop() now closes the drain and clears log_path (close already unlinks, so the old exists-then-clear path no longer fired). New tests/test_regression_cmplog_fifo_stop.py: regression (fails before, passes after), adversarial double-stop, falsification for file sink.
• Copilot: collector fixture now requests monkeypatch, so stop() tears down before monkeypatch undoes. Cross-test leakage did not reproduce (autouse _env_isolation in conftest resets env), but order was wrong within the test; verified with --setup-show.

cmplog tests: 199 passed. ruff clean; lizard clean on the new file.

🤖 Generated with Claude Code

https://claude.ai/code/session_01QWiz6zR3X7BQXuQT2m45G4

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Generated by Claude Code

Summary by Sourcery

Close the cmplog FIFO drain during collector shutdown to prevent resource leaks.

Bug Fixes:

• Ensure stopping the cmplog collector closes the FIFO drain, releases its file descriptors, stops its thread, and clears the log path.

Tests:

• Add regression coverage for FIFO cleanup, repeated stopping, and file-sink behavior.

[sourcery-ai]

Reviewer's Guide

Fix cmplog FIFO resource leaks by closing the drain during collector shutdown, stopping its thread, releasing both FIFO descriptors, and clearing shutdown state; add targeted regression coverage for cleanup, idempotency, file sinks, and fixture teardown ordering.

Sequence diagram for cmplog collector shutdown cleanup

sequenceDiagram
    participant Collector as CmplogCollector
    participant Drain as _FifoDrain
    participant FIFO as FIFO resources
    participant OS as OS

    Collector->>Collector: stop()
    alt FIFO sink configured
        Collector->>Drain: close()
        Drain->>Drain: stop drain thread
        Drain->>FIFO: close both file descriptors
        Drain->>OS: unlink FIFO
        Collector->>Collector: clear _fifo
        Collector->>Collector: clear log_path
    else File sink configured
        Collector->>OS: exists(log_path)
        Collector->>OS: unlink(log_path)
    end

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File-Level Changes

Change	Details	Files
Ensure FIFO-backed collectors fully shut down and release resources.	Close the FIFO drain during stop, which terminates its thread and closes both file descriptors. Clear the drain reference and log path, relying on drain close to unlink the FIFO. Preserve safe cleanup for file sinks and repeated stop calls.	src/fuzzer_tool/core/cmplog.py
Add regression coverage for FIFO shutdown behavior and fixture teardown ordering.	Verify FIFO path removal, drain-thread termination, descriptor closure, and state clearing. Cover double-stop behavior and confirm file sinks do not create a drain. Make the collector fixture depend on monkeypatch so teardown occurs before monkeypatch restoration.	tests/test_regression_cmplog_fifo_stop.py tests/test_regression_cmplog_asan_link_order.py

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[sourcery-ai]

Hey - I've reviewed your changes and they look great!

Sourcery assessment

Approved.

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[Copilot]

Copilot review overview

🟢 Approval recommended

No unresolved review issues remain.

Review effort: Lite
Findings: None

What changed in this PR

Fixes cmplog FIFO resource leaks during collector shutdown.

Changes:

• Closes FIFO drain threads and file descriptors in stop().
• Clears FIFO paths safely.
• Adds cleanup, idempotency, and file-sink regression tests.
• Corrects fixture teardown ordering.

File	Description
tests/​test_regression_cmplog_fifo_stop.py	Covers FIFO cleanup and repeated stopping.
tests/​test_regression_cmplog_asan_link_order.py	Ensures teardown precedes monkeypatch restoration.
src/​fuzzer_tool/​core/​cmplog.py	Releases FIFO drain resources during shutdown.

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