Existing researches suggest that the code clone (duplicated code) is one of the factors that degrades the design and the structure of software and lowers the software quality such as readability and changeability. However, the influence of code clones on software quality has not been quantitatively clarified yet.In this paper, we have tried to quantitatively clarify the relation between code clones and the software reliability and maintainability of twenty years old software. As a result, we found that modules having code clones (clone-included modules) are more reliable than modules having no code clone (non-clone modules) on average. Nevertheless, the modules having very large code clones (more than 200 SLOC) are less reliable than non-clone modules. We also found that clone-included modules are less maintainable (having greater revision number on average) than non-clone modules; and, modules having larger code clone are less maintainable than modules having smaller code clone.
Abstract. Maintaining software systems is getting more complex and difficult task. Code clone is one of the factors that make software maintenance more difficult. A code clone is a code portion in source files that is identical or similar to another. If some faults are found in a code clone, it is necessary to correct the faults in its all code clones. We have developed a maintenance support environment, Gemini, which provides the user with the useful functions to analyze the code clones and modify them. However, through case studies, several problems were reported. That is, the clones provided by Gemini were not appropriate to merge into one module. In this paper, we intend to extend the functionality of Gemini to cope with the problems. Finally, we apply the extended Gemini to several software and evaluate the applicability of the new functions.
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