Open Radar

 
Summary:
Accidental retaining CPNavigationSession without cancelling or finishing produces a deadlock on the next session creation. Such behavior isn’t obvious when a developer hasn’t found yet the issue related to the memory management of the first retained session. 

Steps to Reproduce:
1. Create a CPNavigationSession and retain it (for example in property)
2. Create another CPNavigationSession without canceling, finishing or releasing 1st.

In the sample project:

1. Press Plan route
2. In the Preview dialog press Launch button
3. Repeat 1-2 

Expected Results:
An exception or another way to notify that previous session is still active

Actual Results:
Dead lock on [CPMapTemplate startNavigationSessionForTrip:]. The stacktrace:

* thread #1, queue = 'com.apple.main-thread', stop reason = signal SIGSTOP
  * frame #0: 0x000000010f70b1b6 libsystem_kernel.dylib`semaphore_wait_trap + 10
    frame #1: 0x000000010f371cb8 libdispatch.dylib`_dispatch_sema4_wait + 16
    frame #2: 0x000000010f3724c9 libdispatch.dylib`_dispatch_semaphore_wait_slow + 101
    frame #3: 0x0000000108880e92 CarPlay`-[CPMapTemplate startNavigationSessionForTrip:] + 329
    frame #4: 0x0000000108534fa0 CountryRoads`TemplateManager.createNavigationSession(trip=0x0000600003417630, mapTemplate=0x000060000085d4d0, self=0x0000600000d40210) at TemplateManager.swift:156
    frame #5: 0x00000001085376c9 CountryRoads`TemplateManager.mapTemplate(mapTemplate=0x000060000085d4d0, trip=0x0000600003417630, routeChoice=0x00006000034174b0, self=0x0000600000d40210) at TemplateManager.swift:162
    frame #6: 0x0000000108537806 CountryRoads`@objc TemplateManager.mapTemplate(_:startedTrip:using:) at <compiler-generated>:0
    frame #7: 0x0000000108882d75 CarPlay`__58-[CPMapTemplate startTripIdentifier:usingRouteIdentifier:]_block_invoke_2 + 96
    frame #8: 0x00000001088826b0 CarPlay`-[CPMapTemplate _resolveTrip:routeChoice:completion:] + 534
    frame #9: 0x0000000108882cf4 CarPlay`__58-[CPMapTemplate startTripIdentifier:usingRouteIdentifier:]_block_invoke + 147
    frame #10: 0x000000010f370595 libdispatch.dylib`_dispatch_call_block_and_release + 12
    frame #11: 0x000000010f371602 libdispatch.dylib`_dispatch_client_callout + 8
    frame #12: 0x000000010f37e99a libdispatch.dylib`_dispatch_main_queue_callback_4CF + 1541
    frame #13: 0x000000010d9603e9 CoreFoundation`__CFRUNLOOP_IS_SERVICING_THE_MAIN_DISPATCH_QUEUE__ + 9
    frame #14: 0x000000010d95aa76 CoreFoundation`__CFRunLoopRun + 2342
    frame #15: 0x000000010d959e11 CoreFoundation`CFRunLoopRunSpecific + 625
    frame #16: 0x0000000112edb1dd GraphicsServices`GSEventRunModal + 62
    frame #17: 0x000000010b5e181d UIKitCore`UIApplicationMain + 140
    frame #18: 0x0000000108545857 CountryRoads`main at AppDelegate.swift:13
    frame #19: 0x000000010f3e7575 libdyld.dylib`start + 1

Version:
12.1

Notes:
Additional mentioning in the documentation of existing limitation is also missing.

Configuration: