[previous] 1812 [next] An operand of 'essentially character' type is being subtracted from an operand of 'essentially unsigned' type.
Arithmetic type - Balancing

This message is issued whenever an expression of essentially character type is subtracted from an expression of essentially unsigned type.

For example: 


/*PRQA S 1-9999 ++*/
/*PRQA S 1812 --*/

unsigned f1812 (unsigned a, char b)
{
  b = b - a;                /* OK, essential type of RHS is char */
  return a - b;             /* 1812 */
}

MISRA-C:2004 Rules applicable to message 1812:

Rule  6.1  (Required) The plain char type shall be used only for the storage and use of character values.
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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