Note that RVO is mandatory when returning a prvalue since C++17. IME NRVO happens pretty reliably in the simple case, even on low optimisation levels. There i

Note that RVO is mandatory when returning a prvalue since C++17. IME NRVO happens pretty reliably in the simple case, even on low optimisation levels. There is a proposal for mandatory NRVO in some cases. It would be pretty great, but the proposal didn't move forward for quite a while.