std::move

From Cppreference

Defined in header `<utility>`

template< class T > typename std::remove_reference<T>::type&& move( T&& t );		(C++11 feature)

std::move obtains an rvalue reference to its argument.

It is typically used to implement move semantics when invoking functions. When std::move is used the compiler will look for a function overload that takes an rvalue reference. This means that the contents of t will be moved into the function, leaving t as an xvalue.

#include <iostream>
#include <utility>
#include <vector>
#include <string>
int main()
{
    std::string str = "Hello";
    std::vector<std::string> v;
 
    // uses the push_back(const T&) overload, which means 
    // we'll incur the cost of copying str
    v.push_back(str);
    std::cout << "After copy, str is \"" << str << "\"\n";
 
    // uses the rvalue reference push_back(T&&) overload, 
    // which means no strings will copied; instead, the contents
    // of str will be moved into the vector.  This is less
    // expensive, but also means str will now be empty.
    v.push_back(std::move(str));
    std::cout << "After move, str is \"" << str << "\"\n";
 
    std::cout << "The contents of the vector are \"" << v[0]
                                         << "\", \"" << v[1] << "\"\n";
}

Output:

After copy, str is "Hello"
After move, str is ""
The contents of the vector are "Hello", "Hello"

[edit] Complexity

Constant

[edit] See also

forward (C++11)

forwards a function argument
(function template)

move_if_noexcept (C++11)

obtains an rvalue reference if the move constructor does not throw
(function template)

std::move

From Cppreference

Contents

[edit] Parameters

[edit] Return value

[edit] Exceptions

[edit] Example

[edit] Complexity

[edit] See also


noexcept