Large-language models (LLMs) have been leveraged to enhance the capability of automated program repair techniques in recent research. While existing LLM-based program repair techniques compared favorably to other techniques based on heuristics, constraint-solving, and learning in producing high-quality patches, they mainly target bugs that can be corrected by changing a single faulty method, which greatly limits the effectiveness of such techniques in repairing bugs that demand patches spanning across multiple methods. In this work, we propose the PReMM technique to effectively propose patches changing multiple methods. PReMM builds on three core component techniques: the faulty method clustering technique to partition the faulty methods into clusters based on the dependence relationship among them, enabling a divide-and-conquer strategy for the repairing task; the fault context extraction technique to gather extra information about the fault context which can be utilized to better guide the diagnosis of the fault and the generation of correct patches; the dual-agent-based patch generation technique that employs two LLM-based agents with different roles to analyze the fault more precisely and generate patches of higher-quality. We have implemented the PReMM technique into a tool with the same name and applied the tool to repair real-world bugs from datasets Defects4J V1.2 and V2.0. PReMM produced correct patches for 307 bugs in total. Compared with ThinkRepair, the state-of-the-art LLM-based program repair technique, PReMM correctly repaired 102 more bugs, achieving an improvement of 49.8%.

The problem of automated feedback generation for introductory programming assignments (IPAs) has attracted significant attention with the increasing demand for programming education. While existing approaches, like Refactory, that employ the ”block-by-block” repair strategy have produced promising results, they suffer from two limitations. First, Refactory randomly applies refactoring and mutation operations to correct and buggy programs, respectively, to align their control-flow structures (CFSs), which, however, has a relatively low success rate and often complicates the original repairing tasks. Second, Refactory generates repairs for each basic block of the buggy program when its semantics differs from the counterpart in the correct program, which, however, ignores the different roles that basic blocks play in the programs and often produces unnecessary repairs. To overcome these limitations, we propose the Brafar approach to feedback generation for IPAs. The core innovation of Brafar lies in its novel bidirectional refactoring algorithm and coarse-to-fine fault localization. The former aligns the CFSs of buggy and correct programs by applying semantics-preserving refactoring operations to both programs in a guided manner, while the latter identifies basic blocks that truly need repairs based on the semantics of their enclosing statements and themselves. In our experimental evaluation on 1783 real-life incorrect student submissions from a publicly available dataset, Brafar significantly outperformed Refactory and Clara, generating correct repairs for more incorrect programs with smaller patch sizes in a shorter time.

Developers often neglect to handle exceptions, which leads to exception handling defects that affect the robustness of applications or even cause crashes. To improve the robustness of android applications while reducing the development burden of developers, we present Fixeh and Automatic Detection Tool, as an approach that can automatically detect exception handling defects related to external resources. By implanting exception control codes into the input application, Fixeh helps applications throw exceptions at the specified call position while running the UI test. During running the UI test, Automatic Detection Tool generates a limited number of exception trigger patterns by using suspicious call filtering algorithm and traversal algorithm. After collecting and analyzing the running results under these patterns, the exception handling defects will be detected. We evaluate our approach by applying it to detect anomalies in 6 different types of applications with stable operation. We conducted 1422 rounds of experiments under different exception triggering patterns, and we observed abnormalities in 517 rounds. A comparison with other related work shows that our approach can detect defects more effectively. Through the analysis of our experiments, we confirmed 39 exception handling defects related to external resources. Finally, we summarized three common types of defects from them.