Is Late Propagation a Harmful Code Clone Evolutionary Pattern? An Empirical Study

Osama Ehsan, Liliane Barbour, Foutse Khomh, Ying Zou

Abstract: Two similar code segments, or clones, form a clone pair within a software system. The changes to the clones over time create a clone evolution history. Late propagation is a specific pattern of clone evolution. In late propagation, one clone in the clone pair is modified, causing the clone pair to become inconsistent. The code segments are then re-synchronized in a later revision. Existing work has established late propagation as a clone evolution pattern, and suggested that the pattern is related to a high number of faults. In this chapter, we replicate and extend the work by Barbour et al. (2011 27th IEEE International Conference on Software Maintenance (ICSM). IEEE (2011) [1]) by examining the characteristics of late propagation in 10 long-lived open-source software systems using the iClones clone detection tool. We identify eight types of late propagation and investigate their fault-proneness. Our results confirm that late propagation is the more harmful clone evolution pattern and that some specific cases of late propagations are more harmful than others. We trained machine learning models using 18 clone evolution related features to predict the evolution of late propagation and achieved high precision within the range of 0.91–0.94 and AUC within the range of 0.87–0.91.