Understanding Mirror Bugs in Multiple-Language Projects

As software is widely used in daily life, bugs can introduce catastrophic consequences. Researchers have conducted empirical studies to delve into bug characteristics, exploring topics such as buggy locations, symptoms, causes, and repair patterns. To attract users, many applications have implementations in different languages. If an implementation has a bug, other implementations can have similar bugs. In this article, we call such cross-language clone bugs mirror bugs. Understanding mirror bugs is crucial, as they offer insights into broader bug patterns. Still, no prior study has explored mirror bugs, leaving several research questions unanswered. For instance, can bug fixes in one language help detect and repair bugs in other languages? To address these questions, we conducted the first empirical study analyzing mirror bugs. Our investigation focused on 638 bugs from four projects, implemented in both Java and C#. Our study presents answers to five interesting research questions. For instance, some programmers actively fix mirror bugs even without tool support. Consequently, there is a timely need for tools that assist in detecting mirror bugs. Following this insight, we manually identified and implemented the patches of nine new mirror bugs. Among them, five patches are already accepted by programmers.