[previous] 2120 [next] Integral promotion : unsigned bit-field promoted to signed int.
Arithmetic type - Integral promotion REFERENCE - ISO:C90-6.2.1.1 Characters and Integers

A bit-field of unsigned type is being converted to type signed int under the rules of integral promotion.

This type of conversion will occur whenever an unsigned bit-field which is smaller than an int is used as an operand to one of the following operators:

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

For example: 


/*PRQA S 2017,3131,3408,3447,3602,3621 ++*/

struct ST
{
    unsigned int uib3:3;
    unsigned int uib5:5;
};

extern struct ST     stx;
extern signed int    si;

extern void foo(void)
{
    si = ~stx.uib3;                        /* Message 2120 */
}

See also:

QA·C Source Code Analyser 8.1.2
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