PRE01-A. Use parentheses within macros around variable names

Parenthesize all variable names in macro definitions. See also PRE02.

Non-Compliant Code Example

This CUBE() macro definition is non-compliant because it fails to parethesize the variable names.

#define CUBE(I) (I * I * I)
int c = 81 / CUBE0(2 + 1);

As a result, the invocation

int c = 81 / CUBE0(2 + 1);

expands to

int a = 81 / (2 + 1 * 2 + 1 * 2 + 1);  /* evalutaes to 11 */

while the desired behavior is

int a = 81 / ( (2 + 1) * (2 + 1) * (2 + 1)); /* evaluates to 3 */

Parenthesizing all variable namesthe in the{{CUBE()}} macro allows it to expand correctly (when invoked in this manner).

#define CUBE(I) ( (I) * (I) * (I) )
int c = 81 / CUBE(2 + 1);