Correcting bugs using modern Automated Program Repair (APR) can be both time-consuming and resource-expensive. We describe a program repair approach that aims to improve the scalability of modern APR tools. The approach leverages program reduction in the form of program slicing to eliminate code irrelevant to fixing the bug, which improves the APR tool's overall performance. We investigate slicing's impact on all three phases of the repair process: fault localization, patch generation, and patch validation. Our empirical exploration finds that the proposed approach on average enhances the repair ability of the TBar APR tool, but we also discovered a few cases where it was less successful. Specifically, on examples from the widely used Defects4J dataset, we obtain a substantial reduction in median repair time, which falls from 80 minutes to just under 18 minutes. We conclude that program reduction can improve the performance of APR without degrading repair quality, but this improvement is not universal.

Modern automated program repair (APR) is well-tuned to finding and repairing bugs that introduce observable erroneous behavior to a program. However, a significant class of bugs does not lead to observable behavior (e.g., termination bugs and non-functional bugs). Such bugs can generally not be handled with current APR approaches, so complementary techniques are needed. To stimulate the systematic study of alternative approaches and hybrid combinations, we devise a novel bug classification system that enables methodical analysis of their bug detection power and bug repair capabilities. To demonstrate the benefits, we study the repair of termination bugs in sequential and concurrent programs. Our analysis shows that integrating dynamic APR with formal analysis techniques, such as termination provers and software model checkers, reduces complexity and improves the overall reliability of these repairs. We empirically investigate how well the hybrid approach can repair termination and performance bugs by experimenting with hybrids that integrate different APR approaches with termination provers and execution time monitors. Our findings indicate that hybrid repair holds promise for handling termination and performance bugs. However, the capability of the chosen tools and the completeness of the available correctness specification affects the quality of the patches that can be produced.