QA·C Help - 2896

	2896	Definite: Negative value cast to an unsigned type.

Conversion to unsigned

A definite anomaly has been detected.

The value of an object or a non-constant expression is being cast to an unsigned type and dataflow analysis has determined that the value of the expression is always negative. Is this really intended ? The operation is well defined but is likely at best to be confusing.

The unsigned value which results will the be the value obtained by repeatedly adding or subtracting one more than the maximum value that can be represented in the new type until the value is in the range of the new type.

For example, in the following code, if unsigned char is an 8 bit type, the value assigned to ucx will be the value obtained by repeatedly adding 256 to the value of sia until a non-negative value is achieved..


/*PRQA S 2017,2983,2986,3199,3203,3227,3408 ++*/

void foo(int sia)
{
    unsigned char ucx;

    if (sia < 0)
    {
        ucx = (unsigned char)sia;               /* 2896 */
    }
}

MISRA C:2012 Rules applicable to message 2896:

Dir-1.1 (Required)

Any implementation-defined behaviour on which the output of the program depends shall be documented and understood

See also:

2890 Constant: Negative value implicitly converted to an unsigned type.
2891 Definite: Negative value implicitly converted to an unsigned type.
2892 Apparent: Negative value implicitly converted to an unsigned type.
2893 Suspicious: Negative value implicitly converted to an unsigned type.
2895 Constant: Negative value cast to an unsigned type.
2897 Apparent: Negative value cast to an unsigned type.
2898 Suspicious: Negative value cast to an unsigned type.

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MISRA C:2012 Compliance Module 1.0
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