What are move semantics and rvalue references?

Question

Accepted Answer

**Move semantics** — transfer resources instead of copying.

```cpp
class String {
    char* data;
    size_t len;
public:
    // Move constructor
    String(String&& other) noexcept
        : data(other.data), len(other.len) {
        other.data = nullptr;
        other.len = 0;
    }

// Move assignment
    String& operator=(String&& other) noexcept {
        if (this != &other) {
            delete[] data;
            data = other.data;
            len = other.len;
            other.data = nullptr;
            other.len = 0;
        }
        return *this;
    }
};
```

**`std::move`** — casts to rvalue reference:
```cpp
String a("hello");
String b(std::move(a)); // calls move constructor
```

**`std::forward`** — perfect forwarding in templates.

C++: What are move semantics and rvalue references?