Return value optimizations and side-effects

Question

Return value optimization (RVO) is an optimization technique involving copy elision, which eliminates the temporary object created to hold a function\'s return value in cert

Answer 1

It states it pretty clear, doesn't it? It allows to omit ctor with side effects. So you should never have side effects in ctors or if you insist, you should use techniques which eliminate (N)RVO. As to the second I believe it prohibits NRVO since std::move produces T&& and not T which would be candidate for NRVO(RVO) because std::move removes name and NRVO requires it(thanks to @DyP comment).

Just tested the following code on MSVC:

#include 

class A
{
public:
    A()
    {
        std::cout << "Ctor\n";
    }
    A(const A&)
    {
        std::cout << "Copy ctor\n";
    }
    A(A&&)
    {
        std::cout << "Move\n";
    }

};

A foo()
{
    A a;
    return a;
}

int main() 
{
    A a = foo();
    return 0;
}

it produces Ctor, so we have lost side effects for move ctor. And if you add std::move to foo() you will have NRVO eliminated.