fix(thread-channel): a refused value never reaches the buffer

[EdmondDantes]

ThreadChannel::send() transfers its argument into persistent memory before it takes the lock. The transfer refuses what it cannot copy — a resource, an object with dynamic properties — by releasing the partial graph, leaving the destination IS_UNDEF and throwing. The send did not check for that: it pushed the undefined slot into the buffer and returned true, so the caller got the right exception while the buffer held a value no receiver can interpret.

ThreadPool reads a task as an array, so the next worker to pop that slot died on ZEND_ASSERT(Z_TYPE(task) == IS_ARRAY) at thread_pool.c:347. In a release build the assertion is compiled out and the array fields are read from a value that is not an array.

The send now leaves the buffer untouched and returns false. Every caller already handles that: ThreadChannel::send() rethrows the pending exception, and ThreadPool::submit() and map() release the snapshot, the shared state and the remote future before reporting — thread_pool_throw_closed() keeps a pending exception rather than replacing it, so the transfer error is what the caller sees.

Reproduction

$pool = new Async\\ThreadPool(workers: 1, coroutine: true);
try {
    $pool->submit(static fn () => 1, fopen('php://memory', 'r'));
} catch (Error $e) {
    echo $e->getMessage(), PHP_EOL;   // Cannot transfer a resource between threads
}
$pool->close();

Before: the message is printed and the process aborts (exit 134). After: the message is printed and the process exits 0.

Tests

tests/thread_channel/045-send_refused_value_not_buffered.phpt covers the refusal, the untouched buffer and a following send that succeeds. It fails on main and passes with the fix.

tests/thread_channel, tests/thread_pool and tests/channel — 199 tests, 0 failed. The full suite is unchanged at 3 pre-existing failures in tests/curl and tests/io, which fail identically without this change.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!