Question

pthread_t single_thread ;
pthread_create (&single_thread , NULL , &mywriter , 0) ;
void * ignore ;
pthread_join (single_thread , &ignore) ;

I have this code above, what is the purpose of defining void* ignore and do join of it?
I get a segmentation fault while using it.

Answer 1

The point of the second argument is to get the returning argument from the thread.

Something like an exit code. But since this could also be the address of an object you are returning it is a void** so you can modify the void*. If you look at the signature it is actually a void** that the function expects and you are passing to it.

If you don’t need it, as i think is your case. Just pass null

On return from a successful pthread_join() call with a non-NULL value_ptr argument, the value passed to pthread_exit() by the terminating thread is made available in the location referenced by value_ptr.

Man: pthread_join