[previous] 4394 [next] A composite expression of 'essentially unsigned' type (%1s) is being cast to a different type category, '%2s'.
Arithmetic type - Composite expressions

This message is issued whenever a composite expression of essentially unsigned type has been cast to a different essential type category.

It is a common misconception among programmers that the type in which the arithmetic operation is evaluated is influenced by the cast-to type. Instead, the type of the expression is determined solely from the type of its operands after any integral promotion. Therefore, wraparound may occur, which could be avoided if operands were cast instead.

For example: 


/*PRQA S 1-9999 ++*/
/*PRQA S 4394 --*/

void foo (int b);

int f4394 (unsigned short a)
{
  foo ((int) (a + 1u));    /* 4394 */

  return ((int) (a * 2u)); /* 4394 */
}

MISRA-C:2004 Rules applicable to message 4394:

Rule  10.3  (Required) The value of a complex expression of integer type shall only be cast to a type of the same signedness that is no wider than the underlying type of the expression.

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