Cleaning up copy–paste clones with interactive merging

Copy-paste-modify is a form of software reuse in which developers explicitly duplicate source code. This duplicated source code, amounting to a code clone, is adapted for a new purpose. Copy-paste-modify is popular among software developers, however, empirical evidence shows that it complicates software maintenance and increases the frequency of bugs. To allow developers to use copy-paste-modify without having to worry about these concerns, we propose an approach that automatically merges similar pieces of code by creating suitable abstractions. Because different kinds of abstractions may be beneficial in different contexts, our approach offers multiple abstraction mechanisms, which were selected based on a study of popular open-source repositories. To demonstrate the feasibility of our approach, we have designed and implemented a prototype merging tool for C++ and evaluated it on a number of code clones exhibiting some variation, i.e., near-miss clones, in popular Open Source packages. We observed that maintainers find our algorithmically created abstractions to be largely preferable to the existing duplicated code.