Calloc() not assigning zeros

Question

I want to create a struct which encapsulates a dynamically allocated array. It looks like this:

typedef struct IntArray {
    int *field;
    size_t length;
} IntArray;

Then, I have a function which creates such an IntArray struct:

IntArray *createIntArray(size_t length) {
    IntArray *output;

    if ((output = malloc(sizeof(IntArray))) == NULL) {
        return NULL;
    }

    output->field = calloc(length, sizeof(int));
    output->length = length;

    return output;
}

Here's the main:

int main() {
    size_t size = 10;
    IntArray *test = createIntArray(size);

    for (int i = 0; i < size; i++) {
        printf("%d\n", test[i]);
    }
}

---

I expect calloc() to initialize the memory with zeros, however the output is strange:

---

I think these numbers are memory addresses, but where are they coming from? Every time I start the program, the numbers change but stay on the 1. and 6. positions..

Why is this happening?

EDIT:

I accidentally mixed up calloc and malloc here on stackoverflow, the problem actually occurs with the code above

Answer 1

You are trying to print a struct as an int. A good compiler will warn you abut it if you turn on/up compiler warnings (-Wall if you use gcc).

CreateIntArray creates a single IntArray with field of size length. If you want to print the allocated int array you could use the following:

int main() {
    size_t size = 10;
    IntArray *test = createIntArray(size);

    for (int i = 0; i < size; i++) {
        printf("%d\n", test->field[i]);
    }
}