Implementing and evaluating an exception mechanism for SCOOP

Abstract

Exception handling is an important part of software development. Handling exceptions in concurrent software is even more complicated: There can be asynchronous exceptions, but because of design choices in each language, no exception mechanism can be used everywhere. Several exception mechanisms have been proposed for SCOOP, a concurrent object-oriented programming model. We focus on two of these exception mechanisms, the EiffelSoftware exception mechanism as well as the accountability mechanism. We implemented the accountability mechanism, an exception mechanism which handles exceptions in a more expressive and less restrictive way than the Eiffelsoftware exception mechanism. We also developed variations of that mechanism, making it more expressive. After that, we evaluated both the Eiffelsoftware exception mechanism as well as the accountability mechanism in terms of usability, expressiveness and performance. The evaluation has shown us two points on which we could improve: We refined the accountability mechanism by adding another variant, making it even more expressive and we preserved the types of asynchronous exceptions, thus providing developers with more useful information. Additionally, we implemented the duel mechanism on top of the ordinary exception mechanism, allowing two or more SCOOP processors to duel for a resource, instead of having to wait until the resource is eventually released.