Migrating legacy C++ codebases to newer versions or different platforms often presents opportunities to modernize and improve the code. One area that can benefit from modernization is the error handling mechanisms. In this blog post, we’ll explore some approaches to modernize error handling in migrated C++ code.

Table of Contents

• Introduction
• Rationale for Modernization
• Use of Exceptions
• Error Codes and std::error_code
• Error Handling Libraries
• Conclusion

Introduction

Error handling is a critical aspect of software development. The traditional error handling mechanisms in legacy C++ codebases often involve error codes and manual checks. However, modern C++ offers several techniques and libraries that can simplify and improve error handling.

Rationale for Modernization

Modernizing error handling mechanisms serves several purposes:

1. Simplification: Traditional error code-based approaches can be cumbersome to work with. Modern error handling techniques provide more concise and readable code.
2. Stronger Error Guarantees: Modern techniques, such as exceptions, provide stronger guarantees that errors won’t go unnoticed or lead to resource leaks.
3. Standardization: Standardized error handling mechanisms, like std::error_code, enable better interoperability and integration with other libraries and APIs.

Use of Exceptions

Exceptions provide a powerful and expressive way to handle errors in C++ code. Instead of relying on error codes and manual checks, exceptions allow for more natural flow control, separating the error handling code from the regular code.

try {
    // Code that may throw an exception
} catch (const SomeException& ex) {
    // Handle the exception
}

By throwing and catching exceptions, errors can be propagated up the call stack until they are appropriately handled. Exceptions can carry detailed error information, making it easier to understand and diagnose issues.

Error Codes and std::error_code

Another approach to modernize error handling is to use the std::error_code class. This class, part of the C++ standard library, provides a standardized way to represent and propagate error codes.

std::error_code ec;
// Function call that may produce an error
myFunction(arg1, arg2, ec);

if (ec) {
    // Handle the error
}

Using std::error_code, errors can be checked explicitly, without relying on exceptions. This approach can be especially useful when integrating with existing codebases or interfacing with libraries that use error codes.

Error Handling Libraries

Several open-source libraries are available that provide advanced error handling mechanisms. These libraries often offer additional features like error composition, error categories, and asynchronous error handling.

• boost::outcome is a library that adds a monadic error handling system to C++. It allows for composable, chainable error handling, making error propagation and recovery more expressive.
• folly::Expected is part of Facebook’s Folly library and provides an Expected type that can be used to encapsulate the result or errors of a function call. It can seamlessly interoperate with exceptions and traditional error codes.
• cppcoro is a coroutine library for C++ that provides advanced error handling through asynchronous exceptions. It allows handling errors in an asynchronous and non-blocking manner using familiar exception-handling syntax.

Conclusion

Modernizing error handling mechanisms in migrated C++ code is vital for improving code quality, maintainability, and developer productivity. By leveraging modern techniques like exceptions, std::error_code, or specialized error handling libraries, you can simplify error handling code and provide stronger error guarantees. Choose the approach that best fits your project’s needs and start improving your error handling today.

Did you ever modernize error handling mechanisms in a C++ codebase? Share your experiences! #errorhandling #cpp