Coroutines are a powerful programming abstraction that allows developers to write asynchronous code in a more sequential style. However, when dealing with coroutines in C++, it’s important to handle errors effectively to ensure a robust and reliable application. In this blog post, we will explore some error handling strategies when working with coroutines in C++.

1. Using exceptions

Exceptions are a commonly used error handling mechanism in C++. When working with coroutines, you can throw and catch exceptions within the coroutine to handle errors. This allows you to propagate the error to the calling code and handle it there.

Example:

#include <exception>
#include <experimental/coroutine>

struct Task {
    struct promise_type {
        Task get_return_object() { return {}; }
        std::experimental::suspend_never initial_suspend() { return {}; }
        std::experimental::suspend_never final_suspend() noexcept { return {}; }
        void unhandled_exception() { std::rethrow_exception(std::current_exception()); }
        void return_void() {}
    };
};

Task myCoroutine() {
    try {
        // Coroutine code
        throw std::runtime_error("Something went wrong");
    } catch (const std::exception& ex) {
        // Handle exception
        // Log the error or perform error recovery
    }
}

In the above example, if an exception is thrown within the coroutine, it will be caught in the catch block, allowing you to handle it appropriately.

2. Using error code propagation

Alternatively, you can use error codes to propagate and handle errors in coroutines. This approach is more lightweight compared to exceptions and can be useful in scenarios where exceptions are not desirable or may have performance implications.

Example:

#include <system_error>
#include <experimental/coroutine>

struct Task {
    struct promise_type {
        Task get_return_object() { return {}; }
        std::experimental::suspend_never initial_suspend() { return {}; }
        std::experimental::suspend_never final_suspend() noexcept { return {}; }
        void unhandled_exception() {}
        void return_void() {}
    };
};

Task myCoroutine(std::error_code& ec) {
    if (/* error condition */) {
        ec = std::make_error_code(std::errc::invalid_argument);
        co_return;
    }
    // Coroutine code
}

In this example, the myCoroutine function takes an std::error_code parameter and assigns the appropriate error code if an error condition occurs. The caller can then handle the error code and take necessary actions.

Conclusion

When working with coroutines in C++, it’s crucial to have a solid error handling strategy in place. Whether you choose to use exceptions or error code propagation, understanding how to handle errors effectively will make your applications more robust and maintainable. By carefully designing error handling mechanisms, you can ensure that your coroutines behave predictably and recover gracefully from unexpected situations.

#Cplusplus #ErrorHandling