what are the consequences of having unused functions

Question

I'm wondering what / if any consequences there are in having unused functions in code?

If you hunt down and remove all unused functions and variables would there be any percievable improvement in performance?

Or is it just good practice to remove unused functions and variables would?

Answer 1

Unused functions can't harm performance. They are making the job harder for guys who are maintaining the code. Modern IDE's keep track of unused functions/methods and variables. If it's not a case with the technology that you are speaking about maintainers will have to deal with unused code thinking it's necessary.

Answer 2

Depending on your compiler / linker, it may have no cost at all (and even be removed automatically), or give a small penalty because the code is bigger and gives cache misses. But I'd expect it too be very minor difference.

Edit: Removal cannot be done automatically when there are chances that other code will call it, i.e. library code or other binary that can later be reused. It is also language dependent - if you write JavaScript, everything will get loaded and probably parsed, so this will make a much bigger penalty than in compiled languages.