Static analysis to support the evolution of exception structure in object-oriented systems

Abstract

Exception-handling mechanisms in modern programming languages provide a means to help software developers build robust applications by separating the normal control flow of a program from the control flow of the program under exceptional situations. Separating the exceptional structure from the code associated with normal operations bears some consequences. One consequence is that developers wishing to improve the robustness of a program must figure out which exceptions, if any, can flow to a point in the program. Unfortunately, in large programs, this exceptional control flow can be difficult, if not impossible, to determine.In this article, we present a model that encapsulates the minimal concepts necessary for a developer to determine exception flow for object-oriented languages that define exceptions as objects. Using these concepts, we describe why exception-flow information is needed to build and evolve robust programs. We then describe Jex, a static analysis tool we have developed to provide exception-flow information for Java systems based on this model. The Jex tool provides a view of the actual exception types that might arise at different program points and of the handlers that are present. Use of this tool on a collection of Java library and application source code demonstrates that the approach can be helpful to support both local and global improvements to the exception-handling structure of a system.