CERT C: Rec. INT14-C

Avoid performing bitwise and arithmetic operations on the same data

Description

Rule Definition

Avoid performing bitwise and arithmetic operations on the same data.¹

Polyspace Implementation

The rule checker checks for Bitwise and arithmetic operation on the same data.

Examples

Bitwise and arithmetic operation on the same data

Issue

Bitwise and arithmetic operation on a same data detects statements with bitwise and arithmetic operations on the same variable or expression.

Risk

Mixed bitwise and arithmetic operations do compile. However, the size of integer types affects the result of these mixed operations. Mixed operations also reduce readability and maintainability.

Fix

Separate bitwise and arithmetic operations, or use only one type of operation per statement.

Example - Shift and Addition

unsigned int bitwisearithmix()
{
    unsigned int var = 50;
    var += (var << 2) + 1; //Noncompliant
    return var;
}

This example shows bitwise and arithmetic operations on the variable var. var is shifted by two (bitwise), then increased by 1 and added to itself (arithmetic).

Correction — Arithmetic Operations Only

You can reduce this expression to arithmetic-only operations: var + (var << 2) is equivalent to var * 5.

unsigned int bitwisearithmix()
{
    unsigned int var = 50;
    var = var * 5 +1;
    return var;
}

Check Information

Group: Rec. 04. Integers (INT)

Version History

Introduced in R2019a