Usefulness of const (C++)

Question

I\'m a const fiend, and I strive to make everything as const as possible.

I\'ve tried looking at various dissassembly outputs from const and non const versions of fu

Answer 1

It's pretty rare for const to actually help the compiler optimize. You have to keep in mind that the const_cast can be used anywhere to remove constness from an object (although actually modifying the resulting object isn't always well-defined, it is in some cases, and so the compiler has to be careful about assuming that just because a const object is passed to a function, it won't be modified)

Likewise, the mutable keyword messes things up. You might pass a const object to a function, but what if that object contains a mutable field?

The compiler has to do a lot of work to verify that it's safe to assume that an object is really constant -- and by the time it's done all this verification, the const keyword doesn't really matter, because it could have done all the same analysis on a regular non-const object as well to determine that it isn't being modified and can be treated as constant.

I won't say there aren't a few border cases where the const keyword can enable new optimizations, but in general, const isn't a performance consideration, but a correctness one. Use it to catch more bugs at compile-time, not to speed up your code.