Clones: what is that smell?

Abstract

Clones are generally considered bad programming practice in software engineering folklore. They are identified as a bad smell (Fowler et al. 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" (Fowler et al. 1999). Perhaps we can clone, and breathe easily, at the same time.

Understanding the evolution of Type-3 clones: An exploratory study

“…Researchers have presented evidence that code clones have both positive [14], [25] and negative [18] consequences for maintenance activities and thus, in general, code clones are neither good nor bad. It is also not possible or practical to eliminate certain clone classes from a software system to minimize their potential threats [14].…”

A Survey on Mining Software Repositories

“…Decision tree has been used to predict developers' contribution in [145]. In [65], SVM has been applied for the bug triage and in [147], association rule mining has refactoring [72], [73] API-change [74], [75], [77], [80], [81] change patterns [83]- [88], [90], [160] team-activity developer's contribution [55], [91], [93], [94], [154] experties of developers [96], [97], [149] tool support [98], [99], [128], [151] helpful information [100] comprehension visualization [101], [102], [156] identifiers [104], [105], [153] recording operations [106] validation metrics [45], [107], [157] tool [108] clones [109]- [112], [150], [159] bug [113], [114] development& evolution development [118]- [120] evolution …”

“…However, they could not find systematic relation between them [159]. Rahman et al empirically validated the general negative characteristics of clones [112]. The relations between clones and defect-proneness have been analyzed, and they concluded that most of bugs are not seriously related to clones, clones are less defect-prone than non-cloned codes.…”

Prioritizing the refactoring need for critical component using combined approach

“…It always produces an adverse effect on the system. When anti-pattern occurs in a software system, it is detected by the code smells (Rahman et al, 2012). Code smell is not Antipattern at the deign level, but it can be at the programming level (Carneiro et al, 2010).…”