Effect of Clone Information on the Performance of Developers Fixing Cloned Bugs

Duplicated source code -- clones -- is known to occur frequently in software systems and bears the risk of inconsistent updates of the code. The impact of clones has been investigated mostly by retrospective analysis of software systems. Only little effort has been spent to investigate human interaction when dealing with clones. A previous study by Chatterji and colleagues found that cloned defects are removed significantly more accurately when clone information is provided to the programmers. We conducted a controlled experiment to extend the previous study on the use of clone information by investigating the effect of clone information on the performance of developers in common bug-fixing tasks. The experiment shows that developers are quite capable to compensate missing clone information through testing to provide correct solutions. Clone information does help to detect cloned defects faster, although developers may exploit semantic code relations such as inheritance to uncover cloned defects only slightly slower if they do not have clone information. If cloned defects lurk in semantically unrelated places however, clone information helps to find them faster at statistical significance. Developers without clone information needed 17 minutes longer on average or 140% more time in relative terms to complete the task successfully.