79. Deep Copy Constructor

#include <iostream>
#include <cstdint>
using namespace std;

class SensorData {
private:
    uint8_t* data;  // dynamic array of 8 bytes

public:
    // Constructor: allocate and copy from input array
    SensorData(uint8_t arr[8]) {
        data = new uint8_t[8];
        for (int i = 0; i < 8; i++) {
            data[i] = arr[i];
        }
    }

    // Copy constructor: deep copy
    SensorData(const SensorData& other) {
        data = new uint8_t[8];
        for (int i = 0; i < 8; i++) {
            data[i] = other.data[i];
        }
    }

    // Destructor: free allocated memory
    ~SensorData() {
        delete[] data;
    }

    void setIndex3() {
        data[3] = 99;
    }

    void print() const {
        for (int i = 0; i < 8; i++) {
            cout << (int)data[i] << (i == 7 ? "" : " ");
        }
        cout << endl;
    }
};

int main() {
    uint8_t arr[8];
    for (int i = 0; i < 8; i++) {
        int temp;
        cin >> temp;
        arr[i] = static_cast<uint8_t>(temp);
    }

    SensorData a(arr);
    SensorData b = a;

    b.setIndex3();

    a.print();
    b.print();

    return 0;
}

Explanation & Logic Summary:

• The class owns heap-allocated memory (new[])
• The default copy constructor would perform a shallow copy, causing both objects to share the same buffer
• A correct copy constructor must:
  • Allocate its own buffer
  • Copy all bytes from the source object
• The destructor ensures memory is released once per object

With a deep copy:

• Modifying b does not affect a
• No double-free occurs
• Program behavior is deterministic and safe

Firmware Relevance & Real-World Context:
In embedded systems, this pattern appears in:

• Driver-level data buffers
• Protocol frame builders
• Heap-allocated DMA descriptors
• C++ wrappers over C-based APIs

Incorrect copy behavior can cause:

• Double free
• Heap corruption
• Random system crashes
• Silent data corruption

This problem reinforces:

• Copy constructor semantics
• Deep vs shallow copy
• Resource ownership
• Safe dynamic memory handling in Embedded C++