[previous] 4392 [next] A composite expression of 'essentially floating' type (%1s) is being cast to a wider floating type, '%2s'.
Arithmetic type - Composite expressions

This message is issued whenever a composite expression of essentially floating type has been cast to a wider floating type.

It is a common misconception among programmers that the type in which the composite expression is evaluated is influenced by the wider type. Instead, the type of the expression is determined solely from the type of its operands. Therefore, a loss of precision, overflow or underflow may occur, which could be avoided if the operands were cast to the wider type, or rearranged so that wider operands appear first.

For example: 


/*PRQA S 1-9999 ++*/
/*PRQA S 4392 --*/

void foo (double b);

double f4392 (float a)
{
  foo ((double) (a + 1.0f));    /* 4392 */

  return ((double) (a * 2.0f)); /* 4392 */
}

For the purposes of QAC 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.

MISRA-C:2004 Rules applicable to message 4392:

Rule  10.4  (Required) The value of a complex expression of floating type shall only be cast to a floating type that is narrower or of the same size.

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