Weird issue when making an array of random ints in C

Question

I am currently learning C and I need to write a function to create an array of random integers. I've hit a problem where after creating I try to print and it the first 8 numbers correctly but the rest don't.

int* create(int n) {
    int* array = malloc(n);
    if (!array) return NULL;
    srand(time(NULL));
    for (int i = 0; i < n; i++) {
        array[i] = rand() % 100 + 1;
        printf("num: %i\n", array[i]);
    }

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

    return array;
}

Here is my output for this:

num: 39
num: 2
num: 15
num: 74
num: 80
num: 29
num: 14
num: 16
num: 8
num: 11
num: 2
39
2
15
74
80
29
14
16
973747761
909588276
2614

Answer 1

Issues with your code: malloc expects a size_t, you are directly giving an int. So you should technically do:

    int *array = malloc(sizeof(int) * n);

This basically says that allocate n blocks of sizeof(int) bytes each. What you are doing is allocating n bytes of data. The program is not guaranteed to run always and you are running out of bounds. If you were lucky you would get a Segmentation Fault in one of the runs.