Move Assignment Ownership

Question

Problem: Move Assignment Ownership. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 
#include 
using namespace std;

class Buffer {
private:
    uint8_t* data;
    int size;

public:
    Buffer(int n) : data(nullptr), size(n) {
        data = new uint8_t[size];
    }

    // Disable copy assignment to enforce exclusive ownership
    Buffer& operator=(const Buffer&) = delete;

    // Move assignment operator
    Buffer& operator=(Buffer&& other) noexcept {
        if (this == &other) {
            return *this;
        }

        // Release current resource
        delete[] data;

        // Transfer ownership
        data = other.data;
        size = other.size;

        // Reset source object
        other.data = nullptr;
        other.size = 0;

        return *this;
    }

    ~Buffer() {
        delete[] data;
    }

    void set(int index, uint8_t value) {
        data[index] = value;
    }

    void print() const {
        if (data == nullptr || size == 0) {
            cout << "No data";
        } else {
            for (int i = 0; i < size; i++) {
                cout << (int)data[i];
                if (i != size - 1) cout << " ";
            }
        }
        cout << endl;
    }
};

int main() {
    int N, M;
    cin >> N;

    Buffer A(N);
    for (int i = 0; i < N; i++) {
        int temp;
        cin >> temp;
        A.set(i, (uint8_t)temp);
    }

    cin >> M;
    Buffer B(M);
    for (int i = 0; i < M; i++) {
        int temp;
        cin >> temp;
        B.set(i, (uint8_t)temp);
    }

    A = std::move(B);   // Correct: ownership transfer

    A.print();
    B.print();

    return 0;
}

Explanation & Logic Summary:

This problem enforces exclusive ownership of a dynamically allocated buffer.
Allowing copy assignment would duplicate ownership, leading to double frees or an inconsistent system state.

By deleting the copy assignment operator and implementing a move assignment operator:

The destination object releases its existing buffer
Ownership of the source buffer is transferred
The source object is left in a valid, empty state

This follows the Rule of Five principles and reflects best practices for resource-managing classes in Embedded C++.

Firmware Relevance & Real-World Context:

In firmware and embedded systems, buffers often represent:

DMA memory regions
Network or protocol frames
Sensor data blocks
Hardware-owned memory windows

Move semantics allow zero-copy ownership transfer, improving performance and preventing critical resource duplication bugs—making this a highly relevant real-world Embedded C++ exercise.

Feature	Copy (const Type&)	Move (Type&&)
Operation	Duplicate Data (Deep Copy).	Transfer Pointer (Shallow Copy).
Old Object	Remains valid and unchanged.	Valid but Empty (gutted).
Cost	High (alloc + memcpy).	Near Zero (pointer assignment).
Hardware	Duplicates logic (Bad for drivers).	Transfers ownership (Good for drivers).

Pitfall	Details
❌ Use After Move	Accessing an object after moving from it is undefined logic (usually crashes). `auto b2 = std::move(b1); b1.send();` -> Crash (b1 is empty).
❌ `std::move` doesn't move	`std::move(x)` generates no code. It effectively just casts `x` to `x&&`, telling the compiler "Please try to use the Move Constructor." If you didn't write a Move Constructor, it silently falls back to Copy.
❌ `noexcept`	Always mark move constructors as `noexcept`. If a move can throw an exception, standard containers (like `vector`) will refuse to use it and will Copy instead.
✅ Rule of Five	If you write a custom Destructor, you typically need: Copy Ctor, Copy Assign, Move Ctor, Move Assign.

122. Move Assignment Ownership

Syntax & Usage

Copy vs. Move Visualization

Relevance in Embedded/Firmware

Common Pitfalls (Practical Tips)