An Object-oriented Exception Handling System for an Object-oriented Language

摘要

We present an original exception handling system especially designed for object-oriented languages, making actual information hiding possible and taking into account specific issues of object-oriented languages. It allows association of handlers with expressions as well as with object classes, using a well denned semantics. It offers an object-oriented and extensible representation of exceptions, handlers and knowledge about exceptions. Handlers can specify both resumption and termination. There are no distinctions between system and user denned exceptions. With this system, fault tolerant programs and well specified encapsulations can be written, simple and powerful integration of new user-defined exceptions and secure as well as readable non local moves can be implemented. In this paper, we examine object oriented specific issues related to exception handling. We discuss the exception handling mechanisms available in current object-oriented languages and explain why they do not provide the ability to define fault tolerant encapsulations. Our system description shows how the utilization of the object-oriented formalism solves, in an efficient and simple way, some well known problems related to exception handling such as : how to create exception hierarchies, how to signal fatal or continuable exceptions with the same primitive, how to pass arguments to handlers, and so on.