Error code and exception

[redboltz]

https://github.com/redboltz/async_mqtt/blob/8d3ef845e22de78e19e3542becbd427887c33367/include/async_mqtt/exception.hpp

async_mqtt uses async_mqtt::system_error class for both error code and exception. Error code is typically used as async API's CompletionToken parameter. Exception is typically used as sync part (e.g. packet class constructor) error report.

I think that it is a good way because it is easy to use for error and exception. But perhaps it does not meet to Boost manner.

[redboltz]

Conclusion

Integrate boost::sytem::error_code and boost::system::system_error.
This is the standard way to treat error_code and exceptions.