How Multiple Developers Affect the Evolution of Code Clones

The use of copy and paste in programming causes redundant passages of source code. The effect such clones have on software quality and maintainability in particular has been subject to various studies in the recent past. Although negative effects could not be confirmed in general, a non-negligible number of situations where clones did cause problems has been found. Hence, there may be yet unknown influencing factors that cause these problems. One such factor may be the number of developers involved in the creation and maintenance of a clone. The interaction of multiple developers, unevenly distributed knowledge and communication deficiencies may lead to unwanted inconsistencies and bugs, when the clones are changed. This paper presents an empirical study on long-lived software systems, in which we analyze how many developers are involved in the maintenance exact clones and whether the number of developers affects the likelihood of inconsistent changes. Our results indicate that differences between single-author and multi-author clones exist. Nevertheless, we did not find multiple developers to be the cause of problematic changes to clones.