Background: Code cloning - copying and reusing pieces of source code - is a common phenomenon in software development in practice. There have been several empirical studies on the effects of cloning, but there are contradictory results regarding the connection of cloning and faults. Objective: Our aim is to clarify the relationship between code clones and faults. In particular, we focus on inconsistent (or type-3) clones in this work. Method: We conducted a case study with TWT GmbH where we detected the code clones in three Java systems, set them into relation to information from issue tracking and version control and interviewed three key developers. Results: Of the type-3 clones, 17 contain faults. Developers modified most of the type-3 clones simultaneously and thereby fixed half of the faults in type-3 clones consistently. Type-2 clones with faults all evolved to fixed type-3 clones. Clone length is only weakly correlated with faultiness. Conclusion: There are indications that the developers in two cases have been aware of clones. It might be a reason for the weak relationship between type-3 clones and faults. Hence, it seems important to keep developers aware of clones, potentially with new tool support. Future studies need to investigate if the rate of faults in type-3 clones justifies using them as cues in defect detection.
Jiang, Su and Chiu @cite_9 developed an approach for fault discovery using context-based inconsistencies between clones. They validated their approach on the Linux kernel and Eclipse. They also were able to detect a number of faults: 57 in the Linux kernel and 38 in Eclipse.
@cite_9
1990785546 2098347799 2620081107 2344277659
We present MUSE (MUtation-baSEd fault localization technique), a new fault localization technique based on mutation analysis. A key idea of MUSE is to identify a faulty statement by utilizing different characteristics of two groups of mutants-one that mutates a faulty statement and the other that mutates a correct statement. We also propose a new evaluation metric for fault localization techniques based on information theory, called Locality Information Loss (LIL): it can measure the aptitude of a localization technique for automated fault repair systems as well as human debuggers. The empirical evaluation using 14 faulty versions of the five real-world programs shows that MUSE localizes a fault after reviewing 7.4 statements on average, which is about 25 times more precise than the state-of-the-art SBFL technique Op2. The new hybrid clone detection tool NICAD combines the strengths and overcomes the limitations of both text-based and AST-based clone detection techniques and exploits novel applications of a source transformation system to yield highly accurate identification of cloned code in software systems. In this paper, we present an in-depth study of near-miss function clones in open source software using NICAD. We examine more than 20 open source C, Java and Cn systems, including the entire Linux Kernel, Apache httpd, J2SDK-Swing and db4o and compare their use of cloned code in several different dimensions, including language, clone size, clone similarity, clone location and clone density both by proportion of cloned functions and lines of cloned code. We manually verify all detected clones and provide a complete catalogue of different clones in an online repository in a variety of formats. These validated results can be used as a cloning reference for these systems and as a benchmark for evaluating other clone detection tools. Copyright © 2009 John Wiley & Sons, Ltd. In this paper we provide an empirical study of function clones in more than 20 open source C, Java and Cn systems of varying kinds and sizes including the entire Linux Kernel, using the new hybrid clone detection method, NICAD. We manually verify all the detected clones and provide a complete catalogue of the different clones in an online repository in a variety of formats. Our studies show that there are a large number of near-miss function clones in those systems. Copyright © 2009 John Wiley & Sons, Ltd. Most fault localization techniques take as input a faulty program, and produce as output a ranked list of suspicious code locations at which the program may be defective. When researchers propose a new fault localization technique, they typically evaluate it on programs with known faults. The technique is scored based on where in its output list the defective code appears. This enables the comparison of multiple fault localization techniques to determine which one is better. Previous research has evaluated fault localization techniques using artificial faults, generated either by mutation tools or manually. In other words, previous research has determined which fault localization techniques are best at finding artificial faults. However, it is not known which fault localization techniques are best at finding real faults. It is not obvious that the answer is the same, given previous work showing that artificial faults have both similarities to and differences from real faults. We performed a replication study to evaluate 10 claims in the literature that compared fault localization techniques (from the spectrum-based and mutation-based families). We used 2995 artificial faults in 6 real-world programs. Our results support 7 of the previous claims as statistically significant, but only 3 as having non-negligible effect sizes. Then, we evaluated the same 10 claims, using 310 real faults from the 6 programs. Every previous result was refuted or was statistically and practically insignificant. Our experiments show that artificial faults are not useful for predicting which fault localization techniques perform best on real faults. In light of these results, we identified a design space that includes many previously-studied fault localization techniques as well as hundreds of new techniques. We experimentally determined which factors in the design space are most important, using an overall set of 395 real faults. Then, we extended this design space with new techniques. Several of our novel techniques outperform all existing techniques, notably in terms of ranking defective code in the top-5 or top-10 reports. We consider the problem of identifying the source of failure in a network after receiving alarms or having observed symptoms. To locate the root cause accurately and timely in a large communication system is challenging because a single fault can often result in a large number of alarms, and multiple faults can occur concurrently. In this paper, we present a new fault localization method using a machine-learning approach. We propose to use logistic regression to study the correlation among network events based on end-to-end measurements. Then based on the regression model, we develop fault hypothesis that best explains the observed symptoms. Unlike previous work, the machine-learning algorithm requires neither the knowledge of dependencies among network events, nor the probabilities of faults, nor the conditional probabilities of fault propagation as input. The “low requirement” feature makes it suitable for large complex networks where accurate dependencies and prior probabilities are difficult to obtain. We then evaluate the performance of the learning algorithm with respect to the accuracy of fault hypothesis and the concentration property. Experimental results and theoretical analysis both show satisfactory performance.