Heap-Free Polymorphic Driver

Question

Problem: Heap-Free Polymorphic Driver. Solve this hands-on electronics task on EWskills.

Accepted Answer

#include 
using namespace std;

class Driver {
public:
    virtual void startTransfer() = 0;
    virtual ~Driver() {}
};

class SpiDriver : public Driver {
public:
    void startTransfer() {
        cout << "SPI transfer started" << endl;
    }
};

class I2cDriver : public Driver {
public:
    void startTransfer() {
        cout << "I2C transfer started" << endl;
    }
};

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

    SpiDriver spi;
    I2cDriver i2c;

    Driver& driver = (mode == 0)
                        ? static_cast(spi)
                        : static_cast(i2c);

    driver.startTransfer();

    return 0;
}

Explanation & Logic Summary

Both driver objects are created on the stack, ensuring deterministic lifetime.
A base-class reference is used to refer to the selected driver at runtime.
Virtual dispatch ensures the correct derived implementation executes.
No heap allocation is involved, making the design safe for embedded systems.

Firmware Relevance & Real-World Context

In real embedded firmware systems:

Heap usage is often forbidden or tightly restricted
Drivers are commonly instantiated during system initialization
Runtime selection of peripherals is still required

Using stack-allocated objects with polymorphic references provides:

Deterministic memory usage
Predictable object lifetime
Zero heap fragmentation risk

This problem demonstrates a production-grade embedded C++ technique that is essential for firmware running on resource-constrained systems.

150. Heap-Free Polymorphic Driver