I implemented a multithreaded app, but there was a thread-related crash in the app, I don't understand why this happened, the corresponding stack trace is as follows.
Thread 15 Crashed:: Dispatch queue: com.apple.root.default-qos
0 libsystem_kernel.dylib 0x1a849ad98 __pthread_kill + 8
1 libsystem_pthread.dylib 0x1a84cfee0 pthread_kill + 288
2 libsystem_c.dylib 0x1a840a340 abort + 168
3 libc++abi.dylib 0x1a848ab08 abort_message + 132
4 libc++abi.dylib 0x1a847a950 demangling_terminate_handler() + 336
5 libobjc.A.dylib 0x1a8370320 _objc_terminate() + 144
6 libc++abi.dylib 0x1a8489ea4 std::__terminate(void (*)()) + 20
7 libc++abi.dylib 0x1a8489e40 std::terminate() + 64
8 libdispatch.dylib 0x1a830c1c8 _dispatch_client_callout + 40
9 libdispatch.dylib 0x1a831da04 _dispatch_root_queue_drain + 680
10 libdispatch.dylib 0x1a831e104 _dispatch_worker_thread2 + 164
11 libsystem_pthread.dylib 0x1a84cc324 _pthread_wqthread + 228
12 libsystem_pthread.dylib 0x1a84cb080 start_wqthread + 8
