int x = 10;, x is an lvalue).10 + 20, temporary strings).COPY vs MOVE OF HEAP BUFFER:
COPY: Allocate new buffer -> memcpy elements (Expensive $O(N)$)
MOVE: Steal source pointer (dest.ptr = src.ptr; src.ptr = nullptr;) ($O(1)$ Instantaneous!)MyClass(MyClass&& other) noexcept : ptr(other.ptr) { other.ptr = nullptr; }
#include <iostream>
#include <vector>
#include <utility>
class BigBuffer {
private:
size_t size;
int* data;
public:
explicit BigBuffer(size_t s) : size(s), data(new int[s]) {
std::cout << "[Allocated] BigBuffer with " << size << " ints.\n";
}
// Move Constructor: Steals pointer in O(1)
BigBuffer(BigBuffer&& other) noexcept : size(other.size), data(other.data) {
other.size = 0;
other.data = nullptr; // Leave source in valid empty state
std::cout << "[MOVE Constructor] Pointer stolen safely.\n";
}
~BigBuffer() {
delete[] data;
}
// Delete copy constructor to demonstrate pure move semantics
BigBuffer(const BigBuffer&) = delete;
BigBuffer& operator=(const BigBuffer&) = delete;
};
int main() {
std::cout << "Creating initial buffer...\n";
BigBuffer buf1(1000000);
std::cout << "Moving buffer into vector...\n";
std::vector<BigBuffer> container;
container.push_back(std::move(buf1)); // Invokes Move Constructor
std::cout << "Move completed successfully.\n";
return 0;
}noexcept.nullptr).std::move on it.