[previous] 3394 [next] Extra parentheses recommended. A shift, relational or equality operation is the operand of a different operator with the same precedence.
Readability

The order in which operators are processed in this expression is not sufficiently clear and so additional parentheses are recommended. In the absence of parentheses, the sequence is determined by rules of precedence and associativity.

In this expression, there are 2 different shift operators, 2 different relational operators or 2 different equality operators. The 2 operators have the same precedence and so the first operator (the left hand one) is evaluated first. Add parentheses to make this clear.

For example: 


/*PRQA S 502,2017,3198,3199,3203,3401,3408,3447,4112,4131 ++*/

extern int a;
extern int b;
extern int c;

extern void foo(void)
{
    int r;

    r = a << b >> c;                  /* Message 3394 +3390 */
    r = (a << b) >> c;                /* OK                 */

    r = a < b > c;                    /* Message 3394 +3390 */
    r = (a < b) > c;                  /* OK                 */

    r = a == b != c;                  /* Message 3394 +3390 */
    r = (a == b) != c;                /* OK                 */
}

MISRA-C:2004 Rules applicable to message 3394:

Rule  12.1  (Advisory) Limited dependence should be placed on C's operator precedence rules in expressions.

See also:

QA·C Source Code Analyser 8.1
MISRA-C:2004 Compliance Module 3.2
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