内部函数中的malloc导致SIGSEV

Question

I am trying to write a generic queue implementation in C. For the initialization part, this is what I 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 the implementation, I wrote the following:

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

int main(){
  klein_test();
}

While trying to run such test, I got a SIGSEV . Inspecting the execution with gdb , I could see that the error signal was being generated at queue_init 's first call to malloc . What is the cause of such behaviour?

Answer 1

At least write

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

Also it is not clear why there is declaration

void **elements;

instead of just

void *elements;