Sorting a dynamic array in c

I'm trying to create a function in order to create a ascending order list by using "malloc" and "realloc".

Here is the structure:

struct sorted_dyn_array {
  int *array;
  int length;
  int capacity;
};

returns a pointer to a sorted_dyn_array structure, allocated on the heap

const int BUFFER_INIT_SIZE = 5;
const int KEY_NOT_FOUND = -1;


struct sorted_dyn_array *arr_create(void) {
   struct sorted_dyn_array *new_arr = malloc(sizeof (struct sorted_dyn_array));
   new_arr->array = malloc(sizeof (int) * BUFFER_INIT_SIZE);
   new_arr->length = 0;
   new_arr->capacity = 5;
   return new_arr;
}

free memory:

void free_arr(struct sorted_dyn_array *arr) {
  free(arr->buffer);
  free(arr);
}

int arr_length(struct sorted_dyn_array * arr) {
  return arr->length;
}

int arr_capacity(struct sorted_dyn_array *arr) {
  return arr->capacity;
}

using binary search find the position for the next number:

int find_pos(int item, int arr[], int len) {
 int low = 0;
 int high = len-1;
 if (arr[0] >= item) {
 return 0;
 }
 if(arr[0] < item) {
 return KEY_NOT_FOUND;
 }
 while (low <= high) {
   int mid = low + (high - low) / 2;
   if (arr[mid] == item) {
   return mid;
   } else if (arr[mid] < item) {
   low = mid + 1;
   } else {
   high = mid - 1;
   }
   if(arr[high] < item) {
   return high;
   }
   }
   return KEY_NOT_FOUND;
 }


int arr_find_successor(struct sorted_dyn_array *arr, int k) {
  int len = arr_length(arr);
  return find_pos(k,arr->buffer,len);  
}

insert a number, if it is already in the list, return false. Otherwise, insert a number into the list then return true

bool arr_insert(struct sorted_dyn_array *arr, int k) {
  int pos = arr_find_successor(arr,k);
  if(arr_length(arr) == arr_capacity(arr)) {
  arr->capacity *= 2;
  arr->array = realloc(arr->buffer, sizeof(int) * arr->capacity);// realloc if the     length exceed the capacity
}
if (pos == KEY_NOT_FOUND) {// If the number is greater than all the number in array,put it at the end
  int l = arr->length;
  arr->array[l] = k;
  arr->length++;
  }
  if (pos != KEY_NOT_FOUND){
   for (int c = arr->length - 1; c >= pos; c--)
      arr->array[c+1] = array->array[c];
      arr->array[pos] = k;
      arr->length++;
   }
   return true;
}

Main function:

int main () {
  struct sorted_dyn_array *myarray = arr_create();

  int next = 0;
  while (scanf("%d",&next) == 1) {
    int next_item = next;
    arr_insert(myarray, next_item);
    printf("%d\n",next_item);

   free_arr(myarray);
 }
}

However, when I try to scanf the second number it says

    int arr_length(struct sorted_dyn_array * arr) {
      return arr->length;
    }

invalid access memory. Can somebody help me out? I spend like a whole afternoon and still cant find where goes wrong. Thanks in advance.