std::move (C++11)

In a Nutshell

Casts an lvalue to an rvalue reference, telling the compiler "this object's resources can be stolen," thereby triggering move construction or move assignment to avoid deep copies.

Header

#include <utility>

Core API Quick Reference

Operation	Signature	Description
Move conversion (since C++14)	template<class T> constexpr std::remove_reference_t<T>&& move(T&& t) noexcept;	Casts object t to an rvalue reference (xvalue)
Perfect forwarding	template<class T> T&& forward(typename std::remove_reference<T>::type& t) noexcept;	Preserves value categories in forwarding reference scenarios, must be used with std::move
Conditional move	template<class T> typename std::conditional<...>::type move_if_noexcept(T& t) noexcept;	Casts to an rvalue if move construction is non-throwing, otherwise returns an lvalue

Minimal Example

#include <iostream>
#include <string>
#include <utility>
#include <vector>
// Standard: C++11
int main() {
    std::string str = "Hello";
    std::vector<std::string> v;
    v.push_back(str);              // 拷贝
    v.push_back(std::move(str));   // 移动，str 变为有效但未指定的状态
    std::cout << v[0] << " " << v[1] << "\n";
    std::cout << "str empty: " << str.empty() << "\n";
}

Embedded Applicability: High

• Zero-overhead abstraction: std::move is essentially static_cast, resolved at compile time with no runtime cost
• Avoids deep copies: Significantly reduces RAM usage and CPU overhead when passing large buffers (such as std::vector<uint8_t>, std::string)
• Works with custom resource classes: Can transfer raw pointer ownership (requires RAII), replacing manual resource handover
• Note that a moved-from object is in a "valid but unspecified" state; we cannot read its value, but we can assign to it or destroy it

Compiler Support

GCC	Clang	MSVC
4.6	3.0	19.0

See Also

• cppreference: std::move

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