Question

I’ve been using a program, compiled using GCC 4.4.1 (ISO C99) and noticed this quirk today. Although it works on target without any problem neither does compiler emit any warning with -Wall.

void mutex_init(mutex_t *mutex)
{
 if(unlikely(mutex->magic == MUTX_MAGIC_CHAR))
    return;

 mutex->owner = NULL;
 mutex->prior = NULL;
 mutex->magic = MUTX_MAGIC_CHAR;
 thread_queue_init(&mutex->queue);
}

shouldn’t it be like

*mutex->owner = NULL;

Answer 1

No, magic->owner is equivalent to (*magic).owner.

The -> operator is meant to work on pointers to structures, while the . operator work on structures directly.