Is there an invalid pthread_t id?

Question

I would like to call pthread_join for a given thread id, but only if that thread has been started. The safe solution might be to add a variable to track which thread where s

Answer 1

Unfortunately, on systems where pthread_t is a pointer, pthread_equal() can return equality even though the two args refer to different threads, e.g. a thread can exit and a new thread can be created with the same pthread_t pointer value.