QA·C Help - 2857

	2857	Apparent: Casting to a signed integer type of insufficient size.

Conversion to signed

An apparent anomaly has been detected. An expression is being cast to a signed type, but examination of the context indicates that the value being converted will sometimes be unrepresentable in this type. The result will be implementation-defined.

For example, an object of type signed char can usually only represent values in the range -128 to 127. In the code shown below, unless the if statement is redundant, the code implies that the value of sia will sometimes exceed 127. If it does, behaviour in the subsequent assignment operation will be implementation-defined.


/*PRQA S 273,1278,2017,2984,2983,2986,3120,3195,3198,3199,3203,3227,3408,3602 ++*/

void foo(signed int sia)
{
    signed char sca;

    if (sia > 200)
    {

    }

    sca = (signed char)sia;             /* 2857*/
}

MISRA-C:2004 Rules applicable to message 2857:

Rule 3.1 (Required)

All usage of implementation-defined behaviour shall be documented.

See also:

2850 Constant: Implicit conversion to a signed integer type of insufficient size.
2851 Definite: Implicit conversion to a signed integer type of insufficient size.
2852 Apparent: Implicit conversion to a signed integer type of insufficient size.
2853 Suspicious: Implicit conversion to a signed integer type of insufficient size.
2855 Constant: Casting to a signed integer type of insufficient size.
2856 Definite: Casting to a signed integer type of insufficient size.
2858 Suspicious: Casting to a signed integer type of insufficient size.

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