[previous] 1821 [next] The %1s operand is non-constant and 'essentially signed' (%2s) but will be implicitly converted to an unsigned type (%3s) in this bitwise operation.
Arithmetic type - Balancing

This message is issued whenever a non-constant expression of essentially signed type has been used as an operand of either &, | or ^ operators, and undergoes a usual arithmetic conversion to an unsigned integer type (the type of the other operand).

For example: 


/*PRQA S 1-9999 ++*/
/*PRQA S 1821 --*/

unsigned f1821 (int a, unsigned b)
{
  b = b & a;                /* 1821 */

  return ((a - 1) | b);     /* 1821 */
}

MISRA-C:2004 Rules applicable to message 1821:

Rule  10.1  (Required) The value of an expression of integer type shall not be implicitly converted to a different underlying type if: a) it is not a conversion to a wider integer type of the same signedness, or b) the expression is complex, or c) the expression is not constant and is a function argument, or d) the expression is not constant and is a return expression

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