Can someone please explain why the output of this code is 3 and not 4?

Question

#define square(x) (x*x)

int main () {
    int x,y=1;
    x=square(y+1);
    printf("%d\n",x);
    return 0;
}

the code is quite clear as is the problem....already answered above. — old_timer, May 06 '20 at 03:50
This is one reason using macros should be avoided in favor of functions. — Some programmer dude, May 06 '20 at 03:51
Does this answer your question? [C macros and use of arguments in parentheses](https://stackoverflow.com/questions/7186504/c-macros-and-use-of-arguments-in-parentheses) — Hong Ooi, May 06 '20 at 03:52
To expand on the comment from @M.M, what is the result of `y+1*y+1`? — Some programmer dude, May 06 '20 at 03:52

score 2 · Answer 1 · answered May 06 '20 at 04:00

The reason is that what preprocessor does about macros is quite like a search-replace. So you get y+1*y+1 which gives three. To avoid such problems

wrap every variable in macro definition with parentheses #define square(x) ((x)*(x))
use functions instead (prefered as less likely to run into random errors)

1 Answers1