Szőke, Gábor

Szőke Gábor

University of Szeged

Finding Matching Source Code Elementsin an AST Using Position InformationGábor SzőkeTo decrease software maintenance cost software development companies use static sourcecode analysis techniques. Static analysis tools are capable of finding potential bugs, anti-patterns, coding rule violations and they can enforce coding style standards. To achieve this thetools create a hierarchical representation of the source code called Abstract Syntax Tree (AST).In this structure each node of the tree denotes a construct occurring in the source code. TheAST can be represented in various ways and most static analysis tools build their own ASTrepresentation, typically which fits them the best for their given purpose.Sometimes it is necessary to create a mapping between two different ASTs, e.g. findingmatching source code elements in an AST using just position information. We met this problemin a project where we developed a refactoring tool which was meant to be able to refactorcoding issues based on source code position. In this study, we present an approach whichaddresses this problem. Our solution takes source code position and type information of a nodefrom one AST and uses this information to reverse search the matching node on the other AST.To make reverse searching possible, a spatial database is used, which is created by transformingthe source code into geometric space. Line numbers and column positions from the AST areused to define areas. These areas are used to create R-trees, where area based reverse searchingis possible.findingsThird-party bug detection tool+*a 3bAST1*Line:p5Column:p38Bugpindicatedby source codepositiondetectionSourcepCodeinput inputRefactoring tool+*a 3bAST2buildpspatialpindex R-TreeinputReverse-search *Line:p5Column:p38Buggy sourcepcodepelementinputoutputoutputTo evaluate our approach we use the output of the PMD [1] source code analyzer tool anduse its bug report’s position information as the source data and then we pick the Columbus [2]AST as target AST to find the matching source code element in the syntax tree. We used thistechnique in a project, where the found element was used as input in an automated refactoringtransformation on the target AST. The transformation modified the syntax tree in a way whichfixed the bug reported by the PMD static analyzer tool. As the final step, the refactored versionof the source code got generated from the target AST and developers could review the changes.The evaluation showed that our approach can be adapted to a real-life scenario, and it canprovide viable results. Our tool was used in a project where it assisted in more than 4,000automated refactorings covering systems ranging from 200 to 2,500 kLOC.References[1] PMD website: https://pmd.github.io/[2] Ferenc, Rudolf and Beszédes, Árpád and Tarkiainen, Mikko and Gyimóthy, Tibor, Columbus– Reverse Engineering Tool and Schema for C++, Proceedings of the 18th International Confer-ence on Software Maintenance (ICSM’02), pp. 172-181, 2002.59

Finding matching source code elements in an AST using position information

http://acta.bibl.u-szeged.hu/61739/1/cscs_2016_060.pdf

Finding matching source code elements in an AST using position information

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University of Szeged