In software engineering, relying on experience can render maintainability expertise into prejudice over time. For example, based on their own experience, some consider JavaScript as inelegant language and hence of lowest maintainability. Such prejudice should not guide decisions without prior empirical validation.
All these studies either used outdated and strongly criticised metrics such as the Halstead metrics, the Maintainability Index or more detailed bug pattern analysis. We concentrated on metrics that are automatically collectable, have been proven in practice to be good indicators for quality and are measurable across languages @cite_14 @cite_35 @cite_34 . Only Koschke and Bazrafshan @cite_7 also investigate cloning in their study on clone rates in code written in C and C++. Yet, they focus only on programming languages and cloning.
@cite_35 @cite_14 @cite_7 @cite_34
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Code cloning has been very often indicated as a bad software development practice. However, many studies appearing in the literature indicate that this is not always the case. In fact, either changes occurring in cloned code are consistently propagated, or cloning is used as a sort of templating strategy, where cloned source code fragments evolve independently. This paper (a) proposes an automatic approach to classify the evolution of source code clone fragments, and (b) reports a fine-grained analysis of clone evolution in four different Java and C software systems, aimed at investigating to what extent clones are consistently propagated or they evolve independently. Also, the paper investigates the relationship between the presence of clone evolution patterns and other characteristics such as clone radius, clone size and the kind of change the clones underwent, i.e., corrective maintenance or enhancement. Clones are generally considered bad programming practice in software engineering folklore. They are identified as a bad smell ( 1999) and a major contributor to project maintenance difficulties. Clones inherently cause code bloat, thus increasing project size and maintenance costs. In this work, we try to validate the conventional wisdom empirically to see whether cloning makes code more defect prone. This paper analyses the relationship between cloning and defect proneness. For the four medium to large open source projects that we studied, we find that, first, the great majority of bugs are not significantly associated with clones. Second, we find that clones may be less defect prone than non-cloned code. Third, we find little evidence that clones with more copies are actually more error prone. Fourth, we find little evidence to support the claim that clone groups that span more than one file or directory are more defect prone than collocated clones. Finally, we find that developers do not need to put a disproportionately higher effort to fix clone dense bugs. Our findings do not support the claim that clones are really a "bad smell" ( 1999). Perhaps we can clone, and breathe easily, at the same time. Cloning of code fragments in large systems is a common practice that may result in redundant code, higher maintenance costs, and less modular systems. The paper examines and evaluates the use of five data and control flow related metrics for identifying similar code fragments. The metrics are used as signatures for a code fragment. Matching on such signatures results in fast matching that can be used to locate instances of code cloning even in the presence of modifications such as changes in variable names, and insertion of statements. The paper takes an information retrieval approach and reports on experiments conducted for retrieving code fragments in three different software systems. There are lots of different software metrics discovered and used for defect prediction in the literature. Instead of dealing with so many metrics, it would be practical and easy if we could determine the set of metrics that are most important and focus on them more to predict defectiveness. We use Bayesian networks to determine the probabilistic influential relationships among software metrics and defect proneness. In addition to the metrics used in Promise data repository, we define two more metrics, i.e. NOD for the number of developers and LOCQ for the source code quality. We extract these metrics by inspecting the source code repositories of the selected Promise data repository data sets. At the end of our modeling, we learn the marginal defect proneness probability of the whole software system, the set of most effective metrics, and the influential relationships among metrics and defectiveness. Our experiments on nine open source Promise data repository data sets show that response for class (RFC), lines of code (LOC), and lack of coding quality (LOCQ) are the most effective metrics whereas coupling between objects (CBO), weighted method per class (WMC), and lack of cohesion of methods (LCOM) are less effective metrics on defect proneness. Furthermore, number of children (NOC) and depth of inheritance tree (DIT) have very limited effect and are untrustworthy. On the other hand, based on the experiments on Poi, Tomcat, and Xalan data sets, we observe that there is a positive correlation between the number of developers (NOD) and the level of defectiveness. However, further investigation involving a greater number of projects is needed to confirm our findings.