Categorizing Faults in Exception Handling: A Study of Open Source Projects

Even though exception handling mechanisms have been proposed as a means to improve software robustness, empirical evidence suggests that exception handling code is still poorly implemented in industrial systems. Moreover, it is often claimed that the poor quality of exception handling code can be a source of faults in a software system. However, there is still a gap in the literature in terms of better understanding exceptional faults, i.e., faults whose causes regard to exception handling. In particular, there is still little empirical knowledge about what are the specific causes of exceptional faults in software systems. In this paper we start to fill this gap by presenting a categorization of the causes of exceptional faults observed in two mainstream open source projects. We observed ten different categories of exceptional faults, most of which were never reported before in the literature. Our results pinpoint that current verification and validation mechanisms for exception handling code are still not properly addressing these categories of exceptional faults.