Blanker: A Refactor-Oriented Cloned Source Code Normalizer

Abstract

Refactoring is widely practiced by developers and has become a key factor in order to increase the maintainability of software. However, code clones pose a threat in any refactor process due to the fact that a developer should edit identical portions of code more than once. Despite the numerous researches in this topic, most of the results are focused on discovering type-3 and type-4 clones, that require an higher effort to be refactored and removed. In this paper we present our tool, Blanker, that searches and unifies equivalent statements available in the language before feeding the source to an existing code clone detector limited to type-2 clones. This step acts as a normalization step and produces refactorable results without the error introduced by potentially unrelated added statements (like in type-3 clones), that would be unsuitable for refactoring purposes, and with added flexibility compared to checking for identical code portions (like in type-2 clones). We used NiCad to detect clones before and after our normalization step and found up to 10% more type-2 clones after our normalization, all of them being refactor candidates.