c - Why is "i" variable getting incremented twice in my program?

Question

One of my friend showed me this program and asked me why is i variable getting incremented twice.

According to my understanding MAX(i++, ++j); in this line i is first send as a parameter and then incremented, so if the initial value of i is 10 then the incremented value should be 11, but it shows the incremented value of i as 12.

Program :

#include<stdio.h>

#define MAX(x,y) (x)>(y)?(x):(y)

void main(void)
{
    int i = 10;
    int j = 5;
    int k = 0;

    k = MAX(i++, ++j);

    printf("%d %d %d",i,j,k);
}

Output :

12 6 11

Can someone please explain me how is the value incremented to 12 ?

Thanks.

Answer 1

MAX is a macro, not a function. In your use case, it expands to:

k = (i++) > (++j) ? (i++) : (++j);