In C++17, Return Value Optimization (RVO) became a language guarantee rather than an optional compiler optimization:

std::vector<int> MakeVector() {
    return std::vector<int>(1000000, 42); // Guaranteed RVO (No copy, no move!)
}

std::vector<int> v = MakeVector();

The compiler constructs the vector directly inside the storage location allocated for v on the caller's stack frame. Neither the copy constructor nor the move constructor is ever invoked!

Crucial tip: Never write return std::move(v); on a local variable being returned by value! Doing so actually inhibits NRVO (Named RVO) and forces a move instead of zero-cost in-place construction.

Returning std::move(local) is one of the most common anti-patterns in junior C++ code.