c - malloc inside function causing SIGSEV -

i trying write generic queue implementation in c. initialization part, have:

struct queue{   int head;   int tail;   int max_size;   int elem_size;   void **elements; };  void queue_init(struct queue** q, int max_size, int elem_size){   *q = malloc(sizeof(struct queue));   (*q)->head = (*q)->tail =0;   (*q)->max_size = max_size;   (*q)->elem_size = elem_size;   (*q)->elements = malloc(max_size * elem_size); } 

to test implementation, wrote following:

void klein_test(void){   struct queue** qp;   queue_init(qp, 1, 1);   return; }  int main(){   klein_test(); } 

while trying run such test, got sigsev. inspecting execution gdb, see error signal being generated @ queue_init 's first call malloc. cause of such behaviour?

at least write

struct queue* qp; queue_init(&qp, 1, 1); 

also not clear why there declaration

void **elements; 

instead of just

void *elements;