Slicing Breaks Polymorphism

#include <iostream>
using namespace std;

class Driver {
public:
    virtual void run() {
        cout << "Generic driver running" << endl;
    }
};

class SpiDriver : public Driver {
public:
    void run() override {
        cout << "SPI driver running" << endl;
    }
};

class I2cDriver : public Driver {
public:
    void run() override {
        cout << "I2C driver running" << endl;
    }
};

// correct: base class reference
void processDriver(Driver& driver) {
    driver.run();
}

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

    SpiDriver spi;
    I2cDriver i2c;

    if (mode == 0) {
        processDriver(spi);
    } else {
        processDriver(i2c);
    }

    return 0;
}

Solving Approach