Prediction of function removal propagation in linux evolution

Software studies on the function level, which is inherently different than coarse-grained investigations, contributes to the deep understanding of the laws of software internal evolution. This paper focuses on the life cycle distribution and the propagation behaviour of removed functions in Linux kernels. After an in-depth analysis of 300 Linux kernels, from Version 2.6.12-rc2 to 3.7-rc6, we found that most removed functions have relatively low life cycles, which indicates that many functions are likely to be removed between two consecutive versions. Our experimental results also show that function removal propagation is closely related to the file containing the functions, function call dependency, and historical information. This motivated us to propose a few heuristics to predict function removal propagation, which are based on the file position, call graph, and historical information in git. Furthermore, we analyzed the impact of removed functions on software structure and found that Linux kernel has a strong resistance to function removal. The life cycle feature and the prediction heuristics presented in this paper can be utilized to facilitate the maintenance of large-scale complex software systems.