Detection of redundant clone relations based on clone subsumption

Clone detection has been presented in the literature at different levels of fragment granularity from functions, to syntactic blocks, to variable length strings of source code or tokens. String matching approaches, prefix and suffix trees, metrics, syntactic approaches and others can be used to compare fragments for similarity. Inclusion relations between source code lines may cause some clone relations to be redundant, when clones code fragments subsume each other. This may occur between nested blocks of source code, for example. An original method to analyze this kind of redundancy in clone relations is presented. The proposed method is based on efficiently combining clone subsumption information together with clone similarity relations on code fragments. The amount of redundancy in clone relations has been evaluated on two open source Java systems, Tomcat and Eclipse. Experimental results are presented. Execution time performance of redundancy analysis is measured and reported. Results are discussed together with further proposed research.

Mots clés

clone structural redundancy analysis, clone detection, software metrics, software analysis, open source code analysis