LANG.STRUCT.UUVAL : Unused Value

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CodeSonar^® 9.2p0

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CodeSecure Inc

LANG.STRUCT.UUVAL : Unused Value

Summary

A variable is assigned a value, but that value is never subsequently used on any execution path.

Note

Warnings for unused values arising from assignments to constants are only issued if configuration parameter REPORT_UNUSED_ASSIGNMENTS_FROM_CONSTANTS is set to Yes. Its factory setting is No, so you will need to explicitly change the setting if you want CodeSonar to issue Unused Value warnings in these cases.

Properties

MisraC2025

MisraC2025:2.2

A project shall not contain dead code

MisraC2023

MisraC2023:2.2

A project shall not contain dead code

Misra2012

Misra2012:2.2

A project shall not contain dead code

Misra2004

Misra2004:14.2

All non-null statements shall either (a) have at least one side-effect however executed, or (b) cause control flow to change

AUTOSARC++14

AUTOSARC++14:A0-1-1

A project shall not contain instances of non-volatile variables being given values that are not subsequently used.

AUTOSARC++14:M0-1-9

There shall be no dead code.

MisraC++2008

MisraC++2008:0-1-6

A project shall not contain instances of non-volatile variables being given values that are never subsequently used.

MisraC++2008:0-1-9

There shall be no dead code.

MisraC++2023

MisraC++2023:0.1.1

A value should not be unnecessarily written to a local object

CWE

CWE:563

Assignment to Variable without Use

CWE:1164

Irrelevant Code

CERT-C

CERT-C:MSC13-C

Detect and remove unused values

JSF++

JSF++:187

All non-null statements shall potentially have a side-effect.

DISA-3r10

DISA-3r10:V-6149

The designer will ensure the application does not contain source code that is never invoked during operation, except for software components and libraries from approved third-party products.

Example

#include <stdlib.h>

int lang_struct_uuval_constant(void){
    int x;
    x = 3;            /* 'Unused Value' warning only issued here if
                       * REPORT_UNUSED_ASSIGNMENTS_FROM_CONSTANTS=Yes,
                       * because the assignment is to a constant.
                       */
    x = 4;
    return x;
}

int lang_struct_uuval_rand(void){
    int x;
    x = rand();       /* 'Unused Value' warning issued here regardless
                       * of setting of REPORT_UNUSED_ASSIGNMENTS_FROM_CONSTANTS,
                       * because the assignment is NOT to a constant.
                       */
    x = 4;
    return x;
}

int lang_struct_uuval_multipath(void){
    int i = rand();   /* 'Unused Value' warning issued here: this value is
                       * overwritten on both branches of the IF statement.
                       */
    int j = rand();                  /* ok: this value is used when k ≥ 5 */
    int k = rand();
    if (k < 5){
        i = k;
        j = 5;
    }
    else {
      i = 6;
    }
    return i + j;
}

Relevant Configuration File Parameters

The following configuration file parameters affect checks for this warning class.