Can't initialize linked list - c

Question

I'm trying to build a stack using a linked list but I get a EXC_BAD_ACCESS error in my linkedListStackInit method;
LinkedList.h
#ifndef LinkedListStack_h
#define LinkedListStack_h
#ifndef __TYPE
#define __TYPE
#define TYPE int
#define TYPE_SIZE sizeof(int)
#endif
#include <stdio.h>
struct Link;
struct LinkedListStack;
void linkedListStackInit(struct LinkedListStack *s);
void push(struct LinkedListStack *s, TYPE data);
void pop(struct LinkedListStack *s);
TYPE top(struct LinkedListStack *s);
int isEmpty(struct LinkedListStack *s);
#endif
LinkedList.c
#include <stdlib.h>
#include "LinkedListStack.h"
struct Link {
TYPE value;
struct Link *next;
};
struct LinkedListStack {
struct Link *firstLink;
};
void linkedListStackInit(struct LinkedListStack *s) {
s->firstLink = 0;
}
void push(struct LinkedListStack *s, TYPE data) {
struct Link *newLink = malloc(sizeof(struct Link));
// Assert?
newLink->next = s->firstLink;
newLink->value = data;
s->firstLink = newLink;
}
void pop(struct LinkedListStack *s) {
struct Link *temp = s->firstLink;
s->firstLink = s->firstLink->next;
free(temp);
}
TYPE top(struct LinkedListStack *s) {
return s->firstLink->value;
}
int isEmpty(struct LinkedListStack *s) {
if(s == NULL) {
return 0;
}
else {
return 1;
}
}
main.c
#include <stdio.h>
#include <stdlib.h>
#include "LinkedListStack.h"
int main(int argc, const char * argv[]) {
struct LinkedListStack *s;
linkedListStackInit(s);
return 0;
}

Answer 1

From your main method you are calling the function linkedListStackInit and passing stack (s) to it. But you haven't allocated memory to s before passing it to the linkedListStackInit function. The function linkedListStackInit doesn't allocate the memory either and tries to assign a value to its "firstlink" member. Try to do the following in your linkedListStackInit function and see if you can proceed further.
s = malloc(sizeof(struct LinkedListStack));