CSHARP.FUNCS.IRV : Ignored Return Value (C#)

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CodeSonar^® 9.2p0

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CodeSecure Inc

CSHARP.FUNCS.IRV : Ignored Return Value (C#)

Summary

The returned value of a non-void method is thrown away but should instead be checked or used.

The return value is the result of the computation of a method. In some cases, it is expected that this return value gets used rather than dropped, since it contains important information about the outcome of the method.

Properties

Example

using System.IO;

namespace DocumentationExamples
{
    public class UnusedReturnValue
    {
        private string name;
        private static int counter;
        public UnusedReturnValue(string name)
        {
            this.name = name;
        }
        public UnusedReturnValue(string name, int offset) : this(name)
        {
            counter += offset;
        }
        public static void Main(string[] args)
        {
            Directory.CreateDirectory("dir");   // Ignored Return Value (C#) warning issued here
            UnusedReturnValue t = new UnusedReturnValue("John");
            t.GetName();                        // Ignored Return Value for Pure Function (C#) warning issued here
            new UnusedReturnValue("Joan");      // Ignored Return Value for Pure Function (C#) warning issued here
            new UnusedReturnValue("Albert", 13);                       // ok: has side effect on static field UnusedReturnValue.counter
        }
        public string GetName()
        {
            return name;
        }
    }
}

In this example, the programmer should for instance modify the program as follows.

using System.IO;
using System;

namespace DocumentationExamples
{
    public class UnusedReturnValue
    {
        private string name;
        private static int counter;
        public UnusedReturnValue(string name)
        {
            this.name = name;
        }
        public UnusedReturnValue(string name, int offset) : this(name)
        {
            counter += offset;
        }
        public static void Main(string[] args)
        {
            DirectoryInfo infoDir = Directory.CreateDirectory("dir");
            if (!infoDir.Exists)
            {
                Console.WriteLine("directory could not be created");
                Environment.Exit(0);
            }

            new UnusedReturnValue("Albert", 13);
        }
        public string GetName()
        {
            return name;
        }
    }
}

Resolution

Use the return value of the method or remove the method or constructor call completely, since it has no effect on the heap of the caller, or check if the logic of the code is broken because the return value of a call to a pure method or constructor is not used.

Relevant Configuration File Parameters

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