Should You Return Objects by Constant Value in C ?

Avoiding the Hazards of Returning by Constant Value

The practice of returning objects by constant value in C has been the subject of debate. This article explores the purpose behind this approach and examines the potential drawbacks.

Understanding the Const Qualifier

In the provided code example:

const Object myFunc() {
    return myObject;
}

the const qualifier indicates that the returned object is constant. This means that the object cannot be modified after it is returned.

Arguments for Using Const

Advocates of returning by constant value argue that it:

• Prevents unintended bool casts of the return value.
• Forces explicit assignment of temporary objects.

However, as pointed out in the original question, these benefits can be achieved through other means, such as the explicit keyword for bool conversions.

Drawbacks of Returning by Const

• Inability to Modify Returned Objects: Returning by const value prevents applying non-const operations to the returned object without first assigning it to a non-const variable.
• Incompatibility with Rvalue References: In modern C , returning by non-const value is preferred to take advantage of rvalue references, which improve performance and allow for move semantics.

Conclusion

While there may have been a rationale for returning by constant value in the past, it is no longer considered a recommended practice in modern C . Returning objects by non-const value offers more flexibility and is aligned with best practices involving rvalue references.

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