Should You Use `const` Return Values in Modern C ?

Understanding the Rationale Behind Const Return Values

In this code snippet:

const Object myFunc() {
    return myObject;
}

the keyword const is employed in the return type declaration. It signifies that the returned value is constant, which suggests it cannot be modified after assignment. While this practice has been advocated by various sources, it raises questions regarding its relevance in modern C development.

Pros and Cons of Const Return Values

Historically, returning by const value had certain advantages:

• Prevention of Unintended Bool Casts: This scenario is now addressed more effectively by using the explicit keyword.
• Preventing Modification of Temporary Objects: The const qualification disallows the use of temporary objects without assignment. However, in C 11 and later, rvalue references offer a more efficient approach to handling temporaries, making this concern less significant.

Modern Perspective

In contemporary C , it is generally recommended to return values as non-const. This approach enables the utilization of rvalue references, which optimize the handling of temporary objects and provide better performance.

Conclusion

While there was once a rationale for returning by const value, the introduction of modern C features has rendered this practice obsolete. In most cases, it is preferable to return values as non-const to fully leverage the capabilities of the language.

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