reference or return - best practice [closed]

Question

For example we have encoding function. What is the best practice to use:

void Crypto::encoding(string &input, string &output)
{
    //encoding string
    output = encoded_string;
}

or

string Crypto::encoding(string &input)
{
    //encoding string
    return encoded_string;
}

Should we use reference or return for returning the string? As far as I know returning a string will take some time to initialize a new string that will be returned by return instruction. When working on a referenced variable I don`t waste time to initialize some new variable I just end the function.

Should we mostly use reference and make function return type void? Or we should only return data by reference when we want to return two or more variables and when we need return one variable then use return instruction?

Answer 1

Do not optimize what you did not measure.

Usually it is better (more readable) to return the result of your computation with return. If this takes to long because the object is too fat, you can still revert to return your result via reference parameters, but only after you proved that this will result in significant improvement of performance (measure it). E.g if you only ever encode very short strings and only do that once in a while, the overhead of copying is negligible.

Answer 2

Copying things are usually eliminated since most modern compilers have RVO features. You can take the benefits even without c++11.