why does this C code outputs 1

Question

Is there any reason why:

void function_foo(){
    int k[8];
    function_math(k, 8);
}

void function_math(int *k, int i){
    printf("value: %d", k[i]);
}

The main execute function_foo();

The output will be 1? There's no initialization for elements of matrix k. Maybe something with the length of int in memory?

I am new to C concepts, the pointers and everything.

Answer 1

It is undefined behaviour to evaluate k[8], since k only has 8 elements, not 9.

There is little point arguing about the consequences of undefined behaviour. Anything could happen. Your program is not well-formed.

(Note that it would even be undefined behaviour to evaluate k[0], ..., k[7], since they are unini­tia­lized. You have to write to them first, or initialize the array, such as int k[8] = { 1, 2 };.)