QA·C Help - 3454

	3454	Macro argument contains an increment, decrement or assignment operator.

Preprocessing

This macro argument includes an increment, decrement or assignment operator.

These are operators that generate side effects and there are several reasons why it is unwise to invoke a macro with an argument that induces side effects.

If the argument is evaluated more than once during expansion of the macro, the side effects may be repeated.
There can be confusion about the order in which side effects occur. For example, it is easy ( but incorrect ) to think of a macro call as being similar to a function call, In a function call, all side effects associated with the evaluation of an argument will be complete before the function is called. In the invocation of a macro, the timing of the side-effects associated with the argument may occur after other side-effects which are induced by evaluation of the macro replacement list.

For example:


/*PRQA S 3199,3408,3429,3440,3447,3453 ++ */

#define MAC1(X) ((X) * foo(2))

extern int foo(int p);
extern int g;


extern void func(int sia)
{
    g = MAC1(sia++);                     /* Message 3454 */
}