How can I allocate memory for array inside a function

Question

I am trying to receive a number from the user. And create an array with that number, but, inside a function. Here are my few attempts, I get into run time errors. Help is ve

Answer 1

You have done well upto the point you understood you need to pass a pointer to pointer. But your function signature doesn't take an int **. Either you pass a pointer to pointer and store the allocated memory in it:

void Init(int **pp, int num)
{
    int *p;
    p = malloc(num*sizeof(int));
    if (!p)
    {
        printf("Cannot allocate memory\n");
    }
    *pp = p;
}

And check if the Init() returns a proper pointer:

   Init(&p, num);
   if(p == NULL) {
      /*Memory allocation failed */
   }

---

Or allocate memory and return the pointer:

int* Init(int num)
{
    int *p;
    p = malloc(num*sizeof(int));
    if (!p)
    {
        printf("Cannot allocate memory\n");
    }

    return p;
}

and from main() call as:

int * p = Init(num);
if(p == NULL) {
   /*Memory allocation failed */
}

---

Change the prototype of Init() accordingly.

In any case, you must not free() the pointer in Init(). That just de-allocates memory immediately and you'll be left with a dangling pointer.

And you need to free() in the main() after you are done with it.