QA·C Help - 2791

	2791	Definite: Right hand operand of shift operator is negative or too large.

Shift operations

A definite anomaly has been detected. Examination of the context indicates that the value of the right hand operand (i.e. the number of bits to be shifted) is always out of range. According to the ISO-C standard, if the value is either negative or greater than or equal to the width in bits of the left hand operand (after integral promotion), behavior is undefined.

In the code below, the size of a long is assumed to be 32 bits. If the value of si is less than 0 or greater than 31 the resulting behavior is undefined.


/*PRQA S 1253,1277,1279,1575,1594,2017,2983,2986,3120,3198,3199,3203,3227,3408,4131 ++*/
void f1(unsigned long ul, int si)
{
    if (si > 40)
    {
        ul = ul << si;                /* 2791 */
    }
}

void f2(unsigned long ul, int si)
{
    if (si < 0)
    {
        ul = ul << si;                /* 2791 */
    }
}

See also:

2790 Constant: Right hand operand of shift operator is negative or too large.
2792 Apparent: Right hand operand of shift operator is negative or too large.
2793 Suspicious: Right hand operand of shift operator is negative or too large.

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