Question

I call my program and it is to read a bunch fo integers from the standard input

int main() {
    int* s;
    derp(s);
    return 0;
}

void derp(int *size) {
    scanf("%d", size);
}

why is this code causing a segmentation fault?

Answer 1

int* s;
derp(s);

What does s point to? To random garbage memory since its not initialized. You should do this instead:

int s;
derp(&s);

or you could allocate storage space using malloc:

int* s = malloc( sizeof(int) );
derp(s);
free(s);