Introduction

The goal of this tutorial is to teach you the best practices for exception handling in C++. You will learn several strategies and principles for managing exceptions, ultimately leading to more robust and reliable code.

By the end of this tutorial, you will be able to:
- Understand what exceptions are and why they are important
- Implement exception handling in your C++ programs
- Adopt best practices for exception handling

Prerequisites: Basic understanding of C++ programming.

Step-by-Step Guide

Understanding Exceptions

In C++, exceptions are runtime errors that disrupt the normal flow of execution. Exceptions could be caused by a variety of reasons such as illegal operations, memory leaks, etc.

Exception Handling

Exception handling in C++ is done using three keywords: try, catch, and throw.

• try: Defines a block of code to be monitored for exceptions.
• throw: When an issue is encountered, an exception is thrown.
• catch: Defines a block of code to be executed if an exception occurs in the try block.

Best Practices

1. Throw by Value, Catch by Reference: It's a best practice to throw exceptions by value and catch them by reference. This prevents slicing (losing data from derived types) and allows catching derived types with base references.

2. Use Standard Exceptions: C++ library provides a set of standard exceptions defined in <exception>. Use them whenever possible.

3. Don’t Swallow Exceptions: If a function catches an exception but cannot resolve it, it should rethrow the exception instead of swallowing it.

4. Avoid Catching All Exceptions: Catching all exceptions (catch(...)) should be avoided as it can make debugging difficult.

Code Examples

Example 1: Basic Exception Handling

#include <iostream>

int main() {
    try {
        // Code that may throw an exception
        throw 20;
    }
    catch (int e) {
        std::cout << "An exception occurred. Exception Nr. " << e << '\n';
    }

    return 0;
}

This code snippet will output:

An exception occurred. Exception Nr. 20

Example 2: Re-throwing an Exception

#include <iostream>
#include <exception>

void handleException() {
    try {
        throw std::runtime_error("A problem occurred");
    }
    catch (...) {
        std::cout << "Exception caught in function, re-throwing" << std::endl;
        throw;  // Re-throwing the current exception
    }
}

int main() {
    try {
        handleException();
    }
    catch (const std::exception& e) {
        std::cout << "Exception caught in main: " << e.what() << std::endl;
    }
    return 0;
}

This code snippet will output:

Exception caught in function, re-throwing
Exception caught in main: A problem occurred

Summary

In this tutorial, we covered the basics of exception handling in C++, including throwing and catching exceptions, as well as best practices like throwing by value and catching by reference, using standard exceptions, not swallowing exceptions, and avoiding catching all exceptions.

Next, you should try to apply these practices in your own C++ code. For further reading, refer to the official C++ documentation on exceptions.

Practice Exercises

1. Write a function that throws an exception when a negative number is passed as an argument. Catch and handle this exception.

2. Create a class hierarchy of custom exceptions and write code that demonstrates the "catch by reference" principle.

3. Write a program that demonstrates the use of a standard exception.

Remember that the key to mastering exception handling is practice. Happy coding!