Safe Callback Invocation

Question

Problem: Safe Callback Invocation. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 
using namespace std;

// Callback function implementation
void sensorCallback(int v) {
    cout << "DATA " << v;
}

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

    void (*callback)(int) = nullptr;  // optional callback pointer

    if (flag == 1) {
        callback = sensorCallback;    // register callback
    }

    if (callback == nullptr) {
        cout << "NO CALLBACK";
    } else {
        callback(value);              // safe callback invocation
    }

    return 0;
}

Explanation & Logic Summary:

The callback pointer is initialized to nullptr to represent “no callback registered”
When flag is 1, the callback function address is assigned
Before calling the function pointer, the program checks for nullptr
This prevents undefined behavior caused by invalid function-pointer calls

Firmware Relevance & Real-World Context:

Optional callbacks are common in embedded systems for:
- UART receive handlers
- DMA completion notifications
- Timer expiration callbacks
- ADC conversion completion
Calling a null function pointer can cause hard faults on microcontrollers
Using nullptr checks is a fundamental firmware safety pattern

39. Safe Callback Invocation