Studying the relationship between exception handling practices and post-release defects

Reviewed by Greg Wilson / 2021-09-16
Keywords: Faults, Quality

In this paper from 2018, De Pádua and Shang look at the relationship between anti-patterns in exception handling and error rates in the related code. Unsurprisingly, they find that bad exception handling practices correlate with post-release defects. What makes the work (much) more interesting is that only some anti-patterns correlate in a statistically significant way:

  • The longer the exception handling blocks in a file, the more likely the file is to contain bugs. What's more, the length of the file and the length of its exception handling blocks aren't correlated, so exception handler length really does contain novel information.
  • The Dummy Handler and Generic Catch anti-patterns have a strong statistical relationship to defects.
  • The Ignoring Interrupted Exception and Log and Throw patterns corelated with post-release defects in one of the projects they studied, but not all.

Studies like this one are why I pay attention to software engineering research. Code review checklists tend to grow over time, and the longer they get, the less useful they are. This paper doesn't claim that only four exception handling anti-patterns matter, but since I don't have time to check everything I'd want to when I'm looking over someone's code, knowing which anti-patterns are most important is a real help. It would be great to see this work repeated on a larger sample of projects, and even greater to see whether the same findings hold for programs in Python and other languages.

Finally, my usual grumble about the way abstracts are written in software engineering: the first three sentences of this one are unnecessary, as are the last two, and the authors could have used that space to tell casual browsers which exception handling anti-patterns correlate with post-release defects.

DePadua2018 Guilherme B. de Pádua and Weiyi Shang: "Studying the relationship between exception handling practices and post-release defects". Proceedings of the 15th International Conference on Mining Software Repositories, 10.1145/3196398.3196435.

Modern programming languages, such as Java and C#, typically provide features that handle exceptions. These features separate error-handling code from regular source code and aim to assist in the practice of software comprehension and maintenance. Nevertheless, their misuse can still cause reliability degradation or even catastrophic software failures. Prior studies on exception handling revealed the suboptimal practices of the exception handling flows and the prevalence of their anti-patterns. However, little is known about the relationship between exception handling practices and software quality. In this work, we investigate the relationship between software quality (measured by the probability of having post-release defects) and: (i) exception flow characteristics and (ii) 17 exception handling anti-patterns. We perform a case study on three Java and C# open-source projects. By building statistical models of the probability of post-release defects using traditional software metrics and metrics that are associated with exception handling practice, we study whether exception flow characteristics and exception handling anti-patterns have a statistically significant relationship with post-release defects. We find that exception flow characteristics in Java projects have a significant relationship with post-release defects. In addition, although the majority of the exception handing anti-patterns are not significant in the models, there exist anti-patterns that can provide significant explanatory power to the probability of post-release defects. Therefore, development teams should consider allocating more resources to improving their exception handling practices and avoid the anti-patterns that are found to have a relationship with post-release defects. Our findings also highlight the need for techniques that assist in handling exceptions in the software development practice.