Move Reference Transfer

std::move turns a named object into an rvalue expression so ownership can be transferred.

move_reference_transfer.cpp

#include <iostream>
#include <memory>

int main() {
    int amount = ;

    std::unique_ptr<int> source = std::make_unique<int>(amount);
    std::unique_ptr<int> target = std::move(source);

    std::cout << "sourceEmpty=" << (source == nullptr) << std::endl;
    std::cout << "targetValue=" << *target << std::endl;
    return 0;
}

#include <iostream>
#include <memory>

int main() {
    int amount = ;

    std::unique_ptr<int> source = std::make_unique<int>(amount);
    std::unique_ptr<int> target = std::move(source);

    std::cout << "sourceEmpty=" << (source == nullptr) << std::endl;
    std::cout << "targetValue=" << *target << std::endl;
    return 0;
}

#include <iostream>
#include <memory>

int main() {
    int amount = ;

    std::unique_ptr<int> source = std::make_unique<int>(amount);
    std::unique_ptr<int> target = std::move(source);

    std::cout << "sourceEmpty=" << (source == nullptr) << std::endl;
    std::cout << "targetValue=" << *target << std::endl;
    return 0;
}

move expression `std::move` does not move by itself; it marks an object as movable so a move constructor or move assignment can use it.

moved-from owner A moved-from `std::unique_ptr` becomes empty after its ownership is transferred.