Large language models (LLMs) have revolutionized code completion tasks. IDE plugins such as MarsCode can generate code recommendations, saving developers significant time and effort. However, current evaluation methods for code completion are limited by their reliance on static code benchmarks, which do not consider human interactions and evolving repositories. This paper proposes RepoSim, a novel benchmark designed to evaluate code completion tasks by simulating the evolving process of repositories and incorporating user behaviors. RepoSim leverages data from an IDE plugin, by recording and replaying user behaviors to provide a realistic programming context for evaluation. This allows for the assessment of more complex prompt strategies, such as utilizing recently visited files and incorporating user editing history. Additionally, RepoSim proposes a new metric based on users' acceptance or rejection of predictions, offering a user-centric evaluation criterion. Our preliminary evaluation demonstrates that incorporating users' recent edit history into prompts significantly improves the quality of LLM-generated code, highlighting the importance of temporal context in code completion. RepoSim represents a significant advancement in benchmarking tools, offering a realistic and user-focused framework for evaluating code completion performance.

Universal attack generates image-agnostic perturbation called universal adversarial perturbation (UAP), which can be added to all samples in the data distribution to fool the classifier. However, a universal perturbation will likely mislead the classifier to identify most adversarial examples as the same label, resulting in the imbalance of attack strength between classes. In this paper, we propose class-balanced UAPs that enlarge the dispersion of the predicted labels for adversarial examples. To ensure attack strength and balance simultaneously, we design a novel diversity objective containing probability calibration and penalty regularizer, which fully considers the predicted label distribution between samples and the predicted probability distribution within samples. Furthermore, we apply class-balanced attacks in adversarial training to defend against universal perturbations since the class-balanced UAP provides diverse perturbation directions. We correspondingly reformulate adversarial training from the min-max optimization problem into a new two-stage framework. Experiments on several benchmark datasets demonstrate that the class-balanced attack achieves better performance than the universal attack, while adversarial training with class-balanced UAP achieves state-of-the-art results in clean accuracy and robustness to universal perturbations.

Android apps are ubiquitous and serve many aspects of our daily lives. Ensuring their functional correctness is crucial for their success. To date, we still lack a general and in-depth understanding of functional bugs, which hinders the development of practices and techniques to tackle functional bugs. To fill this gap, we conduct the first systematic study on 399 functional bugs from 8 popular open-source and representative Android apps to investigate the root causes, bug symptoms, test oracles, and the capabilities and limitations of existing testing techniques. This study took us substantial effort. It reveals several new interesting findings and implications which help shed light on future research on tackling functional bugs. Furthermore, findings from our study guided the design of a proof-of-concept differential testing tool, RegDroid, to automatically find functional bugs in Android apps. We applied RegDroid on 5 real-world popular apps, and successfully discovered 14 functional bugs, 10 of which were previously unknown and affected the latest released versions—all these 10 bugs have been confirmed and fixed by the app developers. Specifically, 10 out of these 14 found bugs cannot be found by existing testing techniques. We have made all the artifacts (including the dataset of 399 functional bugs and RegDroid) in our work publicly available at https://github.com/Android-Functional-bugs-study/home.