Explain the function of std::move in C++ and in which cases it is used

The std::move function in C++ does not move an object by itself, but merely converts the argument passed to it into an rvalue reference. This allows the use of move semantics, meaning ownership of the object's resources can be transferred to another object without copying.

std::move is used in situations where it is explicitly indicated that an object can be "moved," such as when returning a local object from a function or passing an object to a move constructor or move assignment operator.

Example:

#include <iostream>
#include <vector>

int main() {
    std::vector<int> v1 = {1, 2, 3};
    std::vector<int> v2 = std::move(v1); // v1 is now empty, resources transferred to v2
    std::cout << "v1 size: " << v1.size() << "\n";
    std::cout << "v2 size: " << v2.size() << "\n";
}

Here, std::move allows avoiding copying elements of the vector, and instead, the internal buffer is moved.

Important: after std::move, the original object is in a valid but unspecified state; it can be safely destroyed or reassigned.