Resolve a question about pthread_rwlock_t


I had try to use pthread_rwlock_t to make a thread safe OperationCache. But I failed. I got a crash:

*** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '-[__NSCFNumber objectForKey:]: unrecognized selector sent to instance 0x8000000000000000'


Find the reason. It was very import for me. I must confirm pthread_rwlock_t is valid to ensure thread safe.


  • maybe: I used pthread_rwlock_t in a wrong way.
  • maybe: “read swift dict” is not thread safe.
  • Luckily. When i google pthread_rwlock_t, I found the difference: I forgot to init pthread_rwlock_t. In honest, it was very strange. I thought lock had been init when i created it.
  • now, follow code will not crash:


  • I got a thread safe OperationCache tool.
  • pthread_rwlock_t is reliable, but must be careful when use.

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