C++ Exception Handling - A Comprehensive Guide

Introduction:
Exception handling is an essential feature in C++ that allows programmers to gracefully manage and respond to unexpected or exceptional situations that may occur during program execution. By incorporating exception handling, developers can maintain better program flow and improve the overall robustness of their code. In this documentation, we will delve into the fundamentals of C++ exception handling, along with code examples and explanations to illustrate its usage effectively.

Table of Contents:

1. What are Exceptions?

   • Definition of exceptions
   • Why use exception handling in C++?

2. Exception Handling Mechanism

   • The role of try, catch, and throw
   • Flow of exception handling

3. Throwing Exceptions

   • Throwing exceptions explicitly
   • Standard exception classes

4. Catching Exceptions

   • Catching specific exceptions
   • Catching multiple exceptions
   • Catch-all (generic) catch block

5. Handling Exceptions

   • Executing cleanup code with finally
   • Nested exception handling

6. Custom Exception Classes

   • Creating user-defined exception classes
   • Inheriting from the standard exception class

Code Example:

cpp
#include <iostream>

// User-defined exception class
class CustomException : public std::exception {
public:
    const char* what() const noexcept override {
        return "Custom Exception: Something went wrong!";
    }
};

int divideNumbers(int a, int b) {
    if (b == 0) {
        throw CustomException();
    }
    return a / b;
}

int main() {
    int num1, num2, result;

    std::cout << "Enter two numbers: ";
    std::cin >> num1 >> num2;

    try {
        result = divideNumbers(num1, num2);
        std::cout << "Result: " << result << std::endl;
    }
    catch (const CustomException& ex) {
        std::cout << "Exception caught: " << ex.what() << std::endl;
    }
    catch (const std::exception& ex) {
        std::cout << "Standard Exception caught: " << ex.what() << std::endl;
    }
    catch (...) {
        std::cout << "Unknown Exception caught!" << std::endl;
    }

    return 0;
}

Explanation:

1. We begin by defining a custom exception class named CustomException, derived from the standard std::exception class. This class provides a customized error message using the what() function.

2. The divideNumbers() function takes two integers as input and attempts to perform division. If the second number (b) is zero, it throws a CustomException.

3. In the main() function, we use the try block to encompass the code that may potentially throw an exception. We call the divideNumbers() function inside the try block.

4. The catch blocks follow the try block, and they are responsible for handling different types of exceptions. If a CustomException is thrown, the first catch block will execute, displaying the custom error message. If any other standard exception is thrown, it will be caught by the second catch block. Finally, if an unknown exception occurs, the last catch block will handle it.

Conclusion:
C++ exception handling allows developers to effectively manage errors and exceptional situations in their code, leading to more robust and reliable programs. By using try, catch, and throw, programmers can gracefully handle unexpected issues and ensure smoother program execution. Understanding and implementing exception handling is crucial for creating high-quality C++ applications.