29. Safe Sensor nullptr Check

#include <iostream>
using namespace std;

int main() {
    int flag;
    cin >> flag;

    int* sensorPtr = nullptr;

    if (flag == 1) {
        sensorPtr = new int;
        cin >> *sensorPtr;
    }

    if (sensorPtr == nullptr) {
        cout << "NO SENSOR";
    } else {
        cout << *sensorPtr;
    }

    delete sensorPtr;
    return 0;
}

Explanation & Logic Summary:

• sensorPtr starts as nullptr to indicate absence of hardware
• Memory is allocated only when the sensor is reported as connected
• A nullptr check prevents unsafe dereferencing
• delete on a null pointer is safe and deterministic

Firmware Relevance & Real-World Context:

• Optional peripherals are common in embedded systems
• nullptr cleanly represents unavailable hardware
• Prevents null dereference crashes (critical firmware faults)
• Common patterns include:
  • HAL optional drivers
  • RTOS object handles
  • Callback and resource pointers