QA·C Help - 2890

	2890	Constant: Negative value implicitly converted to an unsigned type.

Conversion to unsigned

A constant expression with negative value is being implicitly converted to an unsigned type. Is this really intended ? The operation is well defined but is likely at best to be confusing.

The unsigned value which results will 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 char is an 8 bit type, the value assigned to ucx will be 255.


/*PRQA S 277,2017,3211,3408 ++*/

    unsigned char ucx = -1;             /* 2890 */

MISRA-C:2004 Rules applicable to message 2890:

Rule 3.1 (Required)

All usage of implementation-defined behaviour shall be documented.

See also:

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.
2896 Definite: 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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