QA·C Help - 2471

	2471	Unable to identify a loop control variable.

Control flow

QA·C has been unable to identify a loop control variable in this 'for-loop'.

The most common style of 'for-loop' is controlled by a single variable which is initialised in the first expression, tested against a constant value in the second expression and incremented in the third expression. The behaviour of such a loop is conventional and usually well understood. However the C language does not define the concept of a 'loop control variable' and imposes no constraints on the nature of the 3 expressions or the relationships between them.

Message 2472 is generated if there appears to be more than one loop control variable. Message 2471 is generated when QA·C fails altogether to identify loop control variables. Either message is an indication that the loop is controlled in a complex or confusing way.

For example:


/*PRQA S 769,2017,2213,2214,3120,3132,3198,3199,3203,3227,3408,3418,3447 ++*/

extern int ia[100];

extern void f1(int b, int c, int d)
{
    int a;
    int x;

    for ( a = 0; a < 10; ++a) { }                                       /*              */
    for ( a = 0; a < b;  ++a) { }                                       /*              */
    for ( b = 0; a < b;  ++b) { }                                       /*              */
    for ( a = 0; ia[a] < b;  ++a) { }                                   /*              */

    for ( a = 0; a < b;  ++c) { }                                       /* Message 2471 */
    for ( a = 0; b <= c; d++ ) { }                                      /* Message 2471 */
    for ( a = 0; b <= c; a++ ) { }                                      /* Message 2471 */

    for ( a = b, x = c; (a < 10) && (x < 10); ++a, ++x) { }             /* Message 2472 */
}