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Arithmetic type - Integral promotion REFERENCE - ISO:C90-6.2.1.1 Characters and Integers

An operand of type unsigned char is being converted to type signed int under the rules of integral promotion.

This type of conversion will occur if type char is smaller than type int and an expression of type char is used as an operand of the following operators:

Unary + - ~
Multiplicative * / %
Additive + -
Bitwise Shift << >>
Relational < > <= >=
Equality == !=
Bitwise & | ^
Conditional ? : (2nd and 3rd operands)

For example: 


/*PRQA S 3408,3447,3602 ++*/

extern unsigned char ua;
extern unsigned char ub;
extern unsigned char ur;
extern signed int    si;

extern void foo(void)
{
    ur = ua + ub;                             /* Message 2100 */
    si = ~ur;                                 /* Message 2100 */
}

No MISRA-C:2004 Rules applicable to message 2100

See also:

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