Help with segmentation fault please!

I have an assignment to implement a module for something called a SIX Lock. It's basically a complex locking mechanism used for concurrent data access. In any case I'm getting a segmentation fault that I've traced to one line of code but cannot figure out why!

So I have this "class" implementing this SIXlock structure as defined below:

Code:

---

typedef struct
{
        pthread_mutex_t mutex;                        /*our mutex*/
        pthread_cond_t not_locked;                /*cond variable */
        SIXlock_mode_t groupMode;                /*our overall group mode*/
        pthread_t *myThreads;                        /*pointer to threads*/
        SIXlock_mode_t *grantedMode;        /*lock mode of each thread */
        int numThreads;                                /*number of threads in array*/

} SIXlock_lock_t;

---

Yup...I'm using the pthreads library and that's about it.
So I have this create function which starts off like this:

Code:

---

/*-------------------------------------------------------------------------
/Function:        SIXlock_create
/Input:                Pointer to a SIXlock object
/Output:        Returns parameter pointer pointing to created lock
/                Returns SIXlock_result_t notifying the user of the success/failure
-------------------------------------------------------------------------*/
SIXlock_result_t SIXlock_create(SIXlock_lock_t **lockPointer)
{
        int i;
        lockPointer = NULL;

        /*setup memory allocation*/
        lockPointer = (SIXlock_lock_t **)malloc(sizeof( SIXlock_lock_t ));

        /*if error, return result*/
        if(lockPointer == NULL)
                return SIXLOCK_RESULT_ERROR_MALLOC;
       
        /*initialize*/
        pthread_mutex_init(&((*lockPointer)->mutex), NULL);

....

}

---

but when it gets to the:

pthread_mutex_init(&((*lockPointer)->mutex), NULL);

line, it throws a segmentation fault. Can someone please help????

You haven't got the right indirection when setting your lockpointer - it should be

Code:

---

*lockpointer = malloc(...);

---

Note also that you SHOULD NOT cast malloc in C - if you are using a C++ compiler, then it may be acceptable (but then you should be using new/delete!)

Edit: And of course the

Code:

---

lockpointer = NULL;

---

should be

Code:

---

*lockpointer = NULL;

---

--
Mats

Thanks! Wow...don't know how I couldn't figure that one out