QA·C Help - 4399

	4399	An expression which is the result of a ~ or << operation has been cast to a wider type.

Arithmetic type - Casts

This message is issued whenever a composite expression which is the result of a ~ or << operation has been cast to a wider essential type of the same essential type category.

It is a common misconception among programmers that the type in which the bitwise operation is evaluated is influenced by the wider type. Instead, the type of the expression is determined solely from the type of its operands after any integral promotion. Therefore, top bits which could be represented in the wider type may be truncated.

For example:


/*PRQA S 1-9999 ++*/
/*PRQA S 4399 --*/

void foo (unsigned b);

unsigned f4399 (unsigned short a)
{
  foo ((unsigned) (a << 1u)); /* 4399 */

  return ((unsigned) (~a));   /* 4399 */
}

For the purposes of QA·C conversion messages, types are ordered according to the configured size (-s option), by default; hence for a typical 32 bit configuration, types int and long will be considered equivalent. However, when the -strictrank option is specified, types will be ordered according to their rank; consequently int will be considered narrower than long.

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