QA·C Help - 3455

	3455	Macro argument contains a function call.

Preprocessing

This macro argument includes a function call.

A function call may 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 will 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 MAC(P, Q) ((P) * (Q))

extern int foo(void);
extern int x;
extern int g;

extern void func(void)
{
    g = MAC(foo(), x);                     /* Message 3455 */
}

extern int foo(void)
{
    ++x;
    return x;
}