EXC_BAD_ACCESS FlagSynchronizer:63

[m1entus]

Describe the bug
Crash (synchronization issue)

SDK version
9.1.1

OS/platform
iOS

Additional context

Seems this is retain cycle issue:

self.throttler.runThrottled {
      // since going online was throttled, check the last called setOnline value and whether we can go online
      self.go(online: goOnline && self.canGoOnline, reasonOnlineUnavailable: self.reasonOnlineUnavailable(goOnline: goOnline), completion: completion)
}

here you are capturing self inside throttler:
LDClient -> throttler -> runQueue -> runThrottled -> self (LDClient)

this method should look like this:

self.throttler.runThrottled { [weak self] in
      guard let self else {
          completion?()
          return
      }
      // since going online was throttled, check the last called setOnline value and whether we can go online
      self.go(online: goOnline && self.canGoOnline, reasonOnlineUnavailable: self.reasonOnlineUnavailable(goOnline: goOnline), completion: completion)
}

[tanderson-ld]

Hi @m1entus , how frequently are you encountering this issue? Also, thank you for digging deeply and providing an option to fix the issue.

[m1entus]

Just got one crash in Sentry analitycs - so preety rare, but maybe this also can caouse because app is entering background and you are dosing some async action, hard to say really.

[tanderson-ld]

@m1entus , could you provide a rough estimate of number of sessions your customer base runs per day? That will help us evaluate the frequency in a relative percentage.

[m1entus]

@tanderson-ld To be honest it appears only once so far

[Tulakshana]

May be related. So far only once.

Object 0x11dd8b780 of class FlagSynchronizer deallocated with non-zero retain count 2. This object's deinit, or something called from it, may have created a strong reference to self which outlived deinit, resulting in a dangling reference.

abort() called

closure #1 in LDClient.internalIdentify(newContext:completion:)
SIGABRT (ABORT)

Crashed: InternalIdentifyQueue
0  libsystem_kernel.dylib         0xb1dc __pthread_kill + 8
1  libsystem_pthread.dylib        0x7c60 pthread_kill + 268
2  libsystem_c.dylib              0x772d0 abort + 124
3  libswiftCore.dylib             0x391974 swift::fatalError(unsigned int, char const*, ...) + 142
4  libswiftCore.dylib             0x391994 swift::warningv(unsigned int, char const*, char*) + 30
5  libswiftCore.dylib             0x46c030 swift::getLibPrespecializedMetadata(swift::TargetTypeContextDescriptor<swift::InProcess> const*, void const* const*) (.cold.1) + 166
6  libswiftCore.dylib             0x3997a8 swift_deallocPartialClassInstance + 162
7  libswiftCore.dylib             0x3996c8 _swift_release_dealloc + 56
8  libswiftCore.dylib             0x39a63c bool swift::RefCounts<swift::RefCountBitsT<(swift::RefCountInlinedness)1>>::doDecrementSlow<(swift::PerformDeinit)1>(swift::RefCountBitsT<(swift::RefCountInlinedness)1>, unsigned int) + 152
9  LaunchDarkly                   0x416bc closure #1 in LDClient.internalIdentify(newContext:completion:) + 422 (LDClient.swift:422)
10 LaunchDarkly                   0x488c4 partial apply for closure #1 in static NSThread.performOnMain(_:) + 20 (<compiler-generated>:20)
11 LaunchDarkly                   0x3c718 thunk for @escaping @callee_guaranteed () -> () + 20 (<compiler-generated>:20)
12 libdispatch.dylib              0x1b584 _dispatch_client_callout + 16
13 libdispatch.dylib              0x11728 _dispatch_lane_barrier_sync_invoke_and_complete + 56
14 LaunchDarkly                   0x40884 LDClient.internalIdentify(newContext:completion:) + 384 (LDClient.swift:384)
15 LaunchDarkly                   0x3fdfc closure #1 in closure #1 in closure #1 in LDClient._identify(context:sheddable:completion:) + 330 (LDClient.swift:330)
16 LaunchDarkly                   0x482e0 specialized Sequence.forEach(_:) + 192 (<compiler-generated>:192)
17 LaunchDarkly                   0x3fd64 closure #1 in closure #1 in LDClient._identify(context:sheddable:completion:) + 328 (LDClient.swift:328)
18 LaunchDarkly                   0x4b3a4 partial apply for closure #1 in closure #1 in LDClient._identify(context:sheddable:completion:) + 16 (<compiler-generated>:16)
19 libswiftDispatch.dylib         0x1e58 partial apply for thunk for @callee_guaranteed () -> (@out A, @error @owned Error) + 28
20 libswiftDispatch.dylib         0x1fbc thunk for @callee_guaranteed () -> (@out A, @error @owned Error)partial apply + 16
21 libswiftDispatch.dylib         0x1f24 closure #1 in closure #1 in OS_dispatch_queue._syncHelper<A>(fn:execute:rescue:) + 192
22 libswiftDispatch.dylib         0x1e30 partial apply for thunk for @callee_guaranteed () -> () + 28
23 libswiftDispatch.dylib         0x1c8c thunk for @escaping @callee_guaranteed () -> () + 28
24 libdispatch.dylib              0x1b584 _dispatch_client_callout + 16
25 libdispatch.dylib              0x11728 _dispatch_lane_barrier_sync_invoke_and_complete + 56
26 libswiftDispatch.dylib         0x2458 implicit closure #2 in implicit closure #1 in OS_dispatch_queue.sync<A>(flags:execute:) + 196
27 libswiftDispatch.dylib         0x1438 OS_dispatch_queue._syncHelper<A>(fn:execute:rescue:) + 404
28 libswiftDispatch.dylib         0x22b8 OS_dispatch_queue.sync<A>(flags:execute:) + 332
29 LaunchDarkly                   0x3fb0c closure #1 in LDClient._identify(context:sheddable:completion:) + 327 (LDClient.swift:327)
30 LaunchDarkly                   0x8ac34 SheddingQueue.execute() + 56 (SheddingQueue.swift:56)
31 LaunchDarkly                   0x25e28 thunk for @escaping @callee_guaranteed @Sendable () -> () + 28 (<compiler-generated>:28)
32 libdispatch.dylib              0x1aac _dispatch_call_block_and_release + 32
33 libdispatch.dylib              0x1b584 _dispatch_client_callout + 16
34 libdispatch.dylib              0xa2d0 _dispatch_lane_serial_drain + 740
35 libdispatch.dylib              0xadac _dispatch_lane_invoke + 388
36 libdispatch.dylib              0x151dc _dispatch_root_queue_drain_deferred_wlh + 292
37 libdispatch.dylib              0x14a60 _dispatch_workloop_worker_thread + 540
38 libsystem_pthread.dylib        0xa0c _pthread_wqthread + 292
39 libsystem_pthread.dylib        0xaac start_wqthread + 8

Model:iPhone 15 Pro Max (iOS 18.5.0)

pod 'LaunchDarkly', '9.10.0'