Question

Could anybody explain step by step why such arguments ( NULL pointer(s) ) when calling pthread_create like this:

pthread_create(&id_thread1,NULL,thread1,NULL);

result in default attributes for the thread1 ?

I know that pthread.h file is a key factor here.
But unfortunately I do not understand why; the code is way too sophisticated to me.

Thanks in advance!

Answer 1

The signature to pthread_create is:

   int pthread_create(pthread_t *thread, const pthread_attr_t *attr,
                      void *(*start_routine) (void *), void *arg);

The second argument is a pthread_attr_t* pointer. This allows you to set various attributes of the thread, such as scheduling policy or thread stack-size, using a pthread_attr_t object. If attr is NULL then default attributes are used.

The fourth argument is simply a void* pointer that can point to any arbitrary user data to be passed to start_routine when the thread begins. If arg is NULL then a null pointer is passed.