Fix data race in ConcurrentQueue dequeue methods#35
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osalloum wants to merge 1 commit intoaptabase:mainfrom
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Fix data race in ConcurrentQueue dequeue methods#35osalloum wants to merge 1 commit intoaptabase:mainfrom
osalloum wants to merge 1 commit intoaptabase:mainfrom
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The dequeue() and dequeue(count:) methods use queue.sync (a reader lock on the concurrent queue) but call removeFirst() which mutates the array. When two flush() calls run concurrently — e.g. from timerFlushSync and stopPolling — both enter the read lock simultaneously. The first drains the array, the second hits removeFirst() on an empty array, crashing with "Array replace: subrange extends past the end". Fix: use queue.sync(flags: .barrier) for both dequeue methods, matching the barrier pattern already used by the enqueue methods. Fixes aptabase#23
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Summary
dequeue()anddequeue(count:)usequeue.sync(a reader lock on the concurrent queue) but callremoveFirst()which mutates the arrayflush()calls run concurrently (e.g. fromtimerFlushSyncandstopPolling), both enter the read lock simultaneously — the first drains the array, the second crashes withFatal error: Array replace: subrange extends past the endqueue.sync(flags: .barrier)for both dequeue methods, matching the barrier pattern already used by the enqueue methodsCrash backtrace
Fixes #23