Correct crashing issue caused by locking on a object which is replaced inside the lock #220
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Thanks @danielevans |
ckrey
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Jan 4, 2017
> Release date 2017-01-04 [NEW] Support voip applications #243 [NEW] Add public emqtt broker to test suite [NEW] Use signals for synchronouse calls #250 [NEW] Configurable connect-in-foreground behaviour #234 [FIX] CocoaLumberjack related issues. Now on current CocoaLumberjack version [FIX] Documentation update #252 [FIX] Backward compatibility issue #253 [FIX] Publish messages by messageId ascending order when using MQTTInMemoryPersistence #247 [FIX] Adds connectInForeground configuration parameter #223 [FIX] Correct crashing issue caused by locking on a object which is replaced inside the lock #220 [FIX] Use an NSLock instead of locking on an object that is often replaced [FIX] Adding MQTTSessionManager.h to the umbrella header #213 [FIX] sharing the scheme to make the project carthage compatible #198
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Since the MQTT Session Manager is using
@synchronized(self.effectiveSubscriptions)to coordinate updates to the subscriptions but in each case is also replacing theself.effectiveSubscriptionsobject rather than updating it in place a window exists where two threads may obtain locks on different objects despite the fact that both of them are attempting to manipulate the same reference.In our case, this appears to be causing
BAD_ACCESScrashes as multiple threads attempt to deallocate the same object.Replacing the
@synchronizedwith an explicit use of a separateNSLockobject which is not replaced appears to prevent those crashes.