**Course Title:** Modern C++ Programming: Mastering C++ with Best Practices and Advanced Techniques **Section Title:** Error Handling and Exceptions **Topic:** Introduction to exception handling: `try`, `catch`, `throw`. ===================================================== ### Overview of Exception Handling In C++, exception handling is a mechanism for managing runtime errors and unexpected events. It provides a way to handle exceptions in a centralized and structured manner, rather than having to embed error-handling code throughout your program. In this topic, we'll explore the basics of exception handling in C++ and how to use the `try`, `catch`, and `throw` keywords to write robust and reliable code. ### What is an Exception? An exception is an object that represents an error or unexpected event that occurs during the execution of a program. When an exception occurs, the normal flow of the program is interrupted, and control is passed to a specialized block of code, known as a `catch` block, which handles the exception. ### The Throw-Catch Mechanism The throw-catch mechanism in C++ consists of three main keywords: `try`, `catch`, and `throw`. * **`try` block**: This is where you put the code that might throw an exception. It's like a sandbox where you can test your code without affecting the rest of the program. * **`catch` block**: This is where you put the code that handles an exception. It's like a safety net that catches the exception and prevents it from causing any further problems. * **`throw` keyword**: This is used to explicitly throw an exception. It's like a flag that signals to the program that something has gone wrong. Here's a simple example to illustrate the throw-catch mechanism: ```cpp #include <iostream> #include <stdexcept> int divide(int a, int b) { if (b == 0) { // Throw an exception if the divisor is zero throw std::runtime_error("Cannot divide by zero!"); } return a / b; } int main() { try { // Try to divide two numbers int result = divide(10, 0); std::cout << "Result: " << result << std::endl; } catch (const std::runtime_error& e) { // Catch the exception and print an error message std::cerr << "Error: " << e.what() << std::endl; } return 0; } ``` In this example, the `divide` function throws a `runtime_error` exception if the divisor is zero. The `main` function tries to call the `divide` function inside a `try` block and catches the exception in a `catch` block. If an exception occurs, the program prints an error message instead of crashing. ### Exception Handling Basics Here are some key concepts to keep in mind when using exception handling in C++: * **Exception types**: Exceptions are objects of a specific type, such as `std::runtime_error`, `std::invalid_argument`, or `std::out_of_range`. You can also define your own custom exception types using inheritance. * **Exception hierarchies**: Exceptions can be organized into hierarchies, where a base class exception can be caught by a derived class exception. This allows you to catch multiple exceptions with a single catch block. * **Exception propagation**: When an exception is thrown, it is propagated up the call stack until it is caught by a `catch` block. If no catch block is found, the program terminates. ### Best Practices for Using Exceptions Here are some best practices to keep in mind when using exceptions in C++: * **Use exceptions for error handling only**: Exceptions should be used only for error handling and not for normal program flow control. * **Catch by const reference**: When catching an exception, use a const reference to avoid making a copy of the exception object. * **Throw by value**: When throwing an exception, throw by value to ensure that the exception object is copied correctly. * **Use std::exception**: Use the `std::exception` class as the base class for your custom exception types to ensure compatibility with the C++ Standard Library. ### Conclusion In this topic, we've covered the basics of exception handling in C++. We've seen how to use the `try`, `catch`, and `throw` keywords to write robust and reliable code. We've also discussed exception types, exception hierarchies, and exception propagation, and provided some best practices for using exceptions in C++. In the next topic, we'll explore best practices for writing exception-safe code. Do you have any questions or need further clarification on any of the concepts discussed in this topic? Feel free to ask in the comments section. **For further reading:** * [C++ Standard Library documentation](https://en.cppreference.com/w/cpp/error/exception) * [C++ Exceptions Tutorial by tutorialspoint](https://www.tutorialspoint.com/cplusplus/cpp_exceptions_handling.htm) * [C++ Exception Handling by GeeksforGeeks](https://www.geeksforgeeks.org/cpp-exception-handling/) * [Best Practices for Exception Handling in C++ by cppbestpractices](https://cppbestpractices.com/post/66) ### Next Topic: Best Practices for Writing Exception-Safe Code. In the next topic, we'll explore best practices for writing exception-safe code, including how to use RAII, how to avoid leaking resources, and how to write unit tests for exception-safe code.