Example
#define Echo(a) a
#define Echo(a) (a)
I realize there probably isn’t a significant difference here, but why would you ever want to include the a
within parenthesis inside the macro body? How does it alter it?
Suppose you have
#define mul(x, y) x * y
What happens if I say:
mul(a + 5, 6); /* a + 5 * 6 */
Now if I slighlty change the macro:
#define mul(x, y) ((x) * (y))
mul(a + 5, 6); /* ((a + 5) * (6)) */
Remember, the arguments aren't evaluated or anything, only textual substitution is performed.
For an explanation about having the entire macro in parentheses, see the link posted by Nate C-K.