Unnecessary Parenthesis

[00704a-Liber]

In article <2089 at ssc-vax.UUCP> dmg at ssc-vax.UUCP (David Geary) writes:

>"Unnecessary" parenthesis are something I use all the time in macro
>definitions, also.

Most of the parentheses in macros ARE necessary as you have shown (but are
usually not sufficient as I will show).

>Consider:

>#define Square(x)  x*x

[David shows why this macro should be redefined as
#define	Square(x)	((x)*(x))
]

but consider the case where you try the following:

int	x;
x = 2;
(void)printf("The square of %d + 1 is %d.\n", x, Square(++x));

The Square macro does not work correctly because the argument has side
effects (this is why parentheses are not sufficient in macros).
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