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[objective_c] NSInputStream can deadlock #3750
Description
The NSInputStream returned by toNSInputStream will deadlock if native code calls read:maxLength and the Dart isolate backing it exits before providing any data.
CFNetwork does these reads on its single, process-wide com.apple.NSURLConnectionLoader thread. When it hangs, every NSURLSession request in the process stops, and cancelling tasks can't finish.
The exact code location of the lock being held that will never be released.
To reproduce, add this to pkgs/objective_c/test/ns_input_stream_test.dart:
test('isolate exit while read is blocked', () async {
final ready = ReceivePort();
await Isolate.spawn((SendPort sendPort) async {
final controller = StreamController<List<int>>();
final stream = controller.stream.toNSInputStream();
final exitPort = ReceivePort();
sendPort.send((stream, exitPort.sendPort));
await exitPort.first;
Isolate.exit();
}, ready.sendPort);
final (isolatedStream, exitSendPort) =
await ready.first as (NSInputStream, SendPort);
isolatedStream.open();
final readFuture = read(isolatedStream, 10);
await Future<void>.delayed(const Duration(milliseconds: 100));
exitSendPort.send(null);
final (count, data, hasBytesAvailable, status, error) =
await readFuture;
expect(count, -1);
expect(data, isEmpty);
expect(hasBytesAvailable, false);
expect(status, NSStreamStatus.NSStreamStatusError);
expect(error, isNotNull);
isolatedStream.close();
});
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