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AUTOSAR C++14 Rule M0-1-3

A project shall not contain unused variables

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Description

This checker is deactivated in a default Polyspace® as You Code analysis. See Checkers Deactivated in Polyspace as You Code Analysis (Polyspace Access).

Rule Definition

A project shall not contain unused variables.

Rationale

Presence of unused variables indicates that the wrong variable name might be used in the source code. Removing these variables reduces the possibility of the wrong variable being used in further development. Keep padding bits in bitfields unnamed to reduce unused variables in your project.

Polyspace Implementation

The checker flags local or global variables that are declared or defined but not read or written in any source files of the project. This specification also applies to members of structures and classes.

Troubleshooting

If you expect a rule violation but Polyspace does not report it, see Diagnose Why Coding Standard Violations Do Not Appear as Expected.

Examples

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#include <iostream>
struct S {
    unsigned char b1 : 3;
    unsigned char pad: 1;  //Noncompliant
    unsigned char b2 : 4;
};
void init(struct S S_obj)
{
    S_obj.b1 = 0;
    S_obj.b2 = 0;
}

In this example, the bit field pad is used for padding the structure. Therefore, the field is never read or written and causes a violation of this rule. To avoid the violation, use an unnamed field for padding.

#include <iostream>
struct S {
    unsigned char b1 : 3;
    unsigned char : 1;  //Compliant
    unsigned char b2 : 4;
};
void init(struct S S_obj)
{
    S_obj.b1 = 0;
    S_obj.b2 = 0;
}

Check Information

Group: Language Independent Issues
Category: Required, Automated

Version History

Introduced in R2019a

See Also

Topics