Passing two values with parentheses in a single argument function

Question

I got this question from a website asking to give the output of the code

void reverse(int i)
{
    if (i > 5)
        return ;
    printf("%d ", i);
    return reverse((i++, i));
}
int main(int argc, char *argv[]) {
    reverse(1);
    return 0;
}

Output is 1 2 3 4 5

but reverse function is called recursively passing two values within parantheses. How precedence and associativity working here?

Answer 1

, in (i++, i) is a comma operator. It's operands evaluate from left to right. It evaluates i++, value of i get incremented and the value of the expression i++ is discarded and then the incremented value is passed to the function. So, ultimately only a single argument is passed to the function reverse.