title: Ensuring Proper Exception Handling in Modernized C++ Code date: 2021-06-15 tags: c++, exception handling —

Exception handling is a crucial aspect of writing robust and reliable C++ code. It allows developers to gracefully handle and recover from unexpected situations or errors that may occur during program execution. In modernized C++ code, there are several best practices and techniques that can be employed to ensure proper exception handling. This article will explore some of these practices and provide guidance on how to implement them effectively.

1. Use Appropriate Exception Types

In C++, exceptions can be thrown using various types, including built-in types like int or char*, or user-defined types derived from the std::exception class. It is recommended to use user-defined exception types to provide clear and meaningful information about the exceptional condition encountered. This allows for better error reporting and handling.

class FileException : public std::exception {
public:
    const char* what() const noexcept override {
        return "FileException: Error occurred while accessing file.";
    }
};

void readFile(const std::string& filename) {
    std::ifstream file(filename);
    if (!file) {
        throw FileException();
    }
    // ...
}

2. Use RAII (Resource Acquisition Is Initialization)

RAII is a coding technique in which resources, such as file handles or memory allocations, are acquired in the constructor of a class and released in its destructor. This ensures that resources are properly cleaned up, even in the presence of exceptions. By using RAII, the burden of managing resources is transferred to the objects themselves, reducing the chance of resource leaks.

class File {
public:
    File(const std::string& filename) : file_(filename) {
        if (!file_) {
            throw FileException();
        }
    }

    // ... other methods

private:
    std::ifstream file_;
};

void processFile(const std::string& filename) {
    File file(filename);
    // ...
    // Resource will be automatically released even if an exception is thrown.
}

3. Catch Exceptions at the Appropriate Level

It is important to catch exceptions at the appropriate level in the code to handle them effectively. Catching exceptions too early or too late can result in incomplete error handling. Ideally, exceptions should be caught at a level where meaningful recovery or fallback actions can be taken.

void processFiles(const std::vector<std::string>& filenames) {
    for (const auto& filename : filenames) {
        try {
            processFile(filename);
        } catch (const FileException& e) {
            // Log and handle file-related exceptions
        } catch (const std::exception& e) {
            // Log and handle other exceptions
        }
    }
}

By catching exceptions explicitly and handling them appropriately, it becomes easier to diagnose and recover from exceptional scenarios.

4. Provide Sufficient Error Information

When an exception is thrown, it is helpful to provide additional error information to aid in debugging and troubleshooting. This information can be conveyed through the exception message or by including relevant context information. Avoid hiding or masking exceptions with generic error messages, as it hinders the process of identifying the root cause of the exception.

class FileException : public std::exception {
public:
    FileException(const std::string& filename) 
        : filename_(filename) {}

    const char* what() const noexcept override {
        return ("FileException: Error occurred while accessing file: " + filename_).c_str();
    }

private:
    std::string filename_;
};

Conclusion

Proper exception handling is essential for writing reliable and maintainable C++ code. By using appropriate exception types, applying RAII, catching exceptions at the right level, and providing sufficient error information, developers can ensure that their code gracefully handles exceptional situations. Following these best practices not only improves program reliability but also facilitates debugging and troubleshooting.

Remember to handle exceptions with care, and your code will be more robust and resilient to unexpected errors.