C++ copy elision

// -------------------------------------------------
// CMakeLists.txt
// -------------------------------------------------
cmake_minimum_required(VERSION 3.5)
project(cpp4 LANGUAGES CXX)

set(CXX_VER "11")
set(NO_COPY_ELISION 0)

set(CMAKE_CXX_FLAGS "-std=c++${CXX_VER} -O0 -DCXX_VER=${CXX_VER}")
if (NO_COPY_ELISION)
    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fno-elide-constructors")
endif()
set(CMAKE_CXX_STANDARD_REQUIRED ON)
add_executable(cpp4 main.cpp)


// -------------------------------------------------
// main.cpp
// -------------------------------------------------
#include <iostream>
#include <utility>
#include <string>

#define ENABLE_COPY_CTOR
//#define ENABLE_MOVE_CTOR

struct A {
    A() {
        std::cout << "A()" << std::endl;
    }

    A(std::string s): s(s) {
        std::cout << "A(std::string s): " << s << std::endl;
    }

#ifdef ENABLE_COPY_CTOR
    A(const A& other) {
        std::cout << "A(const A& other): " << s << std::endl;
        this->s = other.s;
    }
#else
    #if CXX_VER > 03
        A(const A& other) = delete;
    #endif
#endif

#if defined(ENABLE_MOVE_CTOR) && CXX_VER > 03
    A(A&& other) {
        std::cout << "A(A&& other)" << std::endl;
        this->s = other.s;
        other.s = "";
    }
#else
    #if CXX_VER > 03
        A(A&& other) = delete;
    #endif
#endif
    std::string s;
};

A f(bool c = false) {
    //return c ? A("hello") : A("hello2");
    return A("hello");
}

int main() {
    A a = f();
    std::cout << a.s << std::endl;
}