Understanding the Evolution of Code Clones in Software Systems

Code cloning is a common practice in software development. However, code cloning has both positive aspects such as accelerating the development process and negative aspects such as causing code bloat. After a decade of active research, it is clear that removing all of the clones from a software system is not desirable. Therefore, it is better to manage clones than to remove them. A software system can have thousands of clones in it, which may serve multiple purposes. However, some of the clones may cause unwanted management difficulties and clones like these should be refactored. Failure to manage clones may cause inconsistencies in the code, which is prone to error. Managing thousands of clones manually would be a difficult task. A clone management system can help manage clones and find patterns of how clones evolve during the evolution of a software system. In this research, we propose a framework for constructing and visualizing clone genealogies with change patterns (e.g., inconsistent changes), bug information, developer information and several other important metrics in a software system. Based on the framework we design and build an interactive prototype for a multi-touch surface (e.g., an iPad). The prototype uses a variety of techniques to support understanding clone genealogies, including: identifying and providing a compact overview of the clone genealogies along with their key characteristics; providing interactive navigation of genealogies, cloned source code and the differences between clone fragments; providing the ability to filter and organize genealogies based on their properties; providing a feature for annotating clone fragments with comments to aid future review; and providing the ability to contact developers from within the system to find out more information about specific clones. To investigate the suitability of the framework and prototype for investigating and managing cloned code, we elicit feedback from practicing researchers and developers, and we conduct two empirical studies: a detailed investigation into the evolution of function clones and a detailed investigation into how clones contribute to bugs. In both empirical studies we are able to use the prototype to quickly investigate the cloned source code to gain insights into clone use. We believe that the clone management system and the findings will play an important role in future studies and in managing code clones in software systems

Structured Review of the Evidence for Effects of Code Duplication on Software Quality

This report presents the detailed steps and results of a structured review of code clone literature. The aim of the review is to investigate the evidence for the claim that code duplication has a negative effect on code changeability. This report contains only the details of the review for which there is not enough place to include them in the companion paper published at a conference (Hordijk, Ponisio et al. 2009 - Harmfulness of Code Duplication - A Structured Review of the Evidence)

An Extended Stable Marriage Problem Algorithm for Clone Detection

Code cloning negatively affects industrial software and threatens intellectual property. This paper presents a novel approach to detecting cloned software by using a bijective matching technique. The proposed approach focuses on increasing the range of similarity measures and thus enhancing the precision of the detection. This is achieved by extending a well-known stable-marriage problem (SMP) and demonstrating how matches between code fragments of different files can be expressed. A prototype of the proposed approach is provided using a proper scenario, which shows a noticeable improvement in several features of clone detection such as scalability and accuracy.Comment: 20 pages, 10 figures, 6 table

Code Flows: Visualizing Structural Evolution of Source Code

Understanding detailed changes done to source code is of great importance in software maintenance. We present Code Flows, a method to visualize the evolution of source code geared to the understanding of fine and mid-level scale changes across several file versions. We enhance an existing visual metaphor to depict software structure changes with techniques that emphasize both following unchanged code as well as detecting and highlighting important events such as code drift, splits, merges, insertions and deletions. The method is illustrated with the analysis of a real-world C++ code system.

Code Flows: Visualizing Structural Evolution of Source Code

Understanding detailed changes done to source code is of great importance in software maintenance. We present Code Flows, a method to visualize the evolution of source code geared to the understanding of fine and mid-level scale changes across several file versions. We enhance an existing visual metaphor to depict software structure changes with techniques that emphasize both following unchanged code as well as detecting and highlighting important events such as code drift, splits, merges, insertions and deletions. The method is illustrated with the analysis of a real-world C++ code system.

Structured Review of Code Clone Literature

This report presents the results of a structured review of code clone literature. The aim of the review is to assemble a conceptual model of clone-related concepts which helps us to reason about clones. This conceptual model unifies clone concepts from a wide range of literature, so that findings about clones can be compared with each other