Exception Handling

Unlike C's manual return-code checking, C++ has real exceptions — throw an object (conventionally derived from std::exception), and catch it anywhere up the call stack.

#include <stdexcept>

double divide(double a, double b) {
    if (b == 0) {
        throw std::invalid_argument("Cannot divide by zero");
    }
    return a / b;
}

try {
    std::cout << divide(10, 0) << std::endl;
} catch (const std::invalid_argument &e) {
    std::cout << "Error: " << e.what() << std::endl;
}

Catch by const & (as above) rather than by value — catching by value copies the exception object unnecessarily and can slice a derived exception type down to its base.

Common mistakes

• Throwing an exception out of a destructor — during stack unwinding from another exception, this can terminate the program immediately rather than propagating cleanly.