Crash if MQTTSession stream is created and disposed of quickly

[paulw11]

I was getting a crash in SwiftMQTT if there was a short period between the creation and dispose of an MQTTSessionStream - the problem is that the [weak self] has been released before the async block executes on the sessionQueue. The following check addresses the issue:

sessionQueue.async { [weak self] in
if self != nil {
let currentRunLoop = RunLoop.current
inputStream?.schedule(in: currentRunLoop, forMode: .defaultRunLoopMode)
outputStream?.schedule(in: currentRunLoop, forMode: .defaultRunLoopMode)
inputStream?.open()
outputStream?.open()
if ssl {
let securityLevel = StreamSocketSecurityLevel.negotiatedSSL.rawValue
inputStream?.setProperty(securityLevel, forKey: .socketSecurityLevelKey)
outputStream?.setProperty(securityLevel, forKey: .socketSecurityLevelKey)
}
if timeout > 0 {
DispatchQueue.global().asyncAfter(deadline: .now() + timeout) {
self?.connectTimeout()
}
}

			currentRunLoop.run()
		}
	}
}

[paulw11]

Actually this code doesn't fix it :(

[adolfo]

@paulw11 could you write a failing test that reproduces this issue? A PR that fixes the problem is also appreciated if you find the solution.

[Jeffkenly88]

@adolfo Hi, I'm having the same issue, it happens not regularly, I just had to restart the app multiple times and it happens 1 time out of 10. It crashed with BAD_ACCESS exception on currentRunLoop.run()

[Kerry50407]

I simply moved the let currentRunLoop = RunLoop.current out of the queue scope,
Like this..

let currentRunLoop = RunLoop.current
sessionQueue.async { [weak self] in
inputStream?.schedule(in: currentRunLoop, forMode: .defaultRunLoopMode)
.....
currentRunLoop.run()
}

The app stop crashing.
I guess it happened due to the currentRunLoop is released. (not sure for the root cause)

Hope it helps!

[adolfo]

Resolved in #40