Throwing Exceptions in C++

Exception handling is a crucial aspect of writing robust C++ programs. It allows developers to manage and respond to runtime errors gracefully. In this guide, we'll explore how to throw exceptions in C++.

What is Exception Throwing?

Throwing an exception is the process of signaling that an error or exceptional condition has occurred in your program. It's a way to interrupt the normal flow of execution and transfer control to an error-handling routine.

Basic Syntax

To throw an exception in C++, you use the throw keyword followed by an expression. This expression can be of any type, but it's common to use objects of exception classes.

throw exception_object;
    

Examples of Throwing Exceptions

1. Throwing a Standard Exception

#include <stdexcept>

void divide(int a, int b) {
    if (b == 0) {
        throw std::runtime_error("Division by zero!");
    }
    // Perform division
}
    

2. Throwing a Custom Exception

class CustomException : public std::exception {
public:
    const char* what() const noexcept override {
        return "A custom exception occurred";
    }
};

void riskyFunction() {
    // Some code that might cause an error
    throw CustomException();
}
    

Best Practices for Throwing Exceptions

• Use exceptions for exceptional conditions, not for normal control flow.
• Throw by value, catch by reference. This avoids object slicing and improves performance.
• Use standard exceptions when appropriate, or derive from std::exception for custom exceptions.
• Provide meaningful error messages in your exceptions to aid debugging.
• Be mindful of exception safety and ensure resources are properly managed.

Exception Specifications (Deprecated)

C++98 introduced exception specifications, but they were deprecated in C++11 and removed in C++17. Instead, use noexcept to indicate functions that don't throw exceptions.

void safeFunction() noexcept {
    // This function guarantees it won't throw exceptions
}
    

Related Concepts

To fully understand exception handling in C++, you should also be familiar with:

• C++ Try-Catch Blocks for handling thrown exceptions
• C++ Custom Exceptions for creating your own exception classes
• C++ Exception Specifications for understanding historical context and modern alternatives

Conclusion

Throwing exceptions is a powerful mechanism for error handling in C++. When used judiciously, it can significantly improve the robustness and reliability of your code. Remember to balance exception usage with performance considerations and always strive for exception-safe code.