C++ Pass By Const Reference and Return By Const Reference

Question

I\'m trying to understand if there is any benefit to returning a const reference. I have a factorial function that normally looks like this:

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Answer 1

The const reference is incorrect here - you're returning a reference to a local variable - an un-named temporary here, either 1 or the result of n * factorial(n - 1). Because the reference is to a local variable in the function, by the time the reference gets to the caller, that local variable has already gone out of scope, and is invalid.

Return a const reference to large structured types that you want to avoid a copy to when the reference will survive the exit of the function. Usually, this means returning a reference to an argument or to a member variable (in the case of classes).