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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

Program Dependence Graph Generation and Analysis for Source Code Plagiarism Detection / Generering och analys av programberoendegrafer för detektering av plagiat i källkod

Holma, Niklas January 2012 (has links)
Systems and tools that finds similarities among essays and reports are widely used by todays universities and schools to detect plagiarism. Such tools are however insufficient when used for source code comparisons since they are fragile to the most simplest forms of diguises. Other methods that analyses intermediate forms such as token strings, syntax trees and graph representations have shown to be more effective than using simple textual matching methods. In this master thesis report we discuss how program dependence graphs, an abstract representation of a programs semantics, can be used to find similar procedures. We also present an implementation of a system that constructs approximated program dependence graphs from the abstract syntax tree representation of a program. Matching procedures are found by testing graph pairs for either sub-graph isomorphism or graph monomorphism depending on whether structured transfer of control has been used. Under a scenario based evaluation our system is compared to Moss, a popular plagiarism detection tool. The result shows that our system is more or least as effective than Moss in finding plagiarized procedured independently on the type of modifications used. / System och verktyg som hittar likheter mellan uppsatser och rapporter används i stor omfattning av dagens universitet och skolor för att hitta plagiat bland studenters inlämningar. Sådana verktyg är dock otillräckliga när de används för att jämföra programkod eftersom de är svaga mot de enklaste formerna av modifikationer. Andra metoder som analyserar mellanstegsformer såsom tokensträngar, syntaxträd och grafrepresentationer har visat sig vara mer effektiva än att använda sig av enkla textuella metoder. I denna examensuppsats diskuterar vi hur programberoendegrafer, en abstrakt representation av en programs semantik, kan användas för att hitta jämförelsevis liknande procedurer. Vi presenterar också ett system som konstruerar approximerade programberoendegrafer från det abstrakta syntaxträdet av ett program. Matchande procedurer hittas genom att testa grafpar för antingen sub-graf isomorfism eller monomorfism beroende på om strukturerad byte av kontrolflöde har använts. I en scenariobaserad utvärdering jämför vi vårt system mot Moss, ett populärt verktyg för att detektera plagiat. Resultaten visar att vårt system är lika eller mer effektivt som Moss att detektera plagierade procedurer oberoende av de typer av modifikationer som använts.
2

A Study of Backward Compatible Dynamic Software Update

January 2015 (has links)
abstract: Dynamic software update (DSU) enables a program to update while it is running. DSU aims to minimize the loss due to program downtime for updates. Usually DSU is done in three steps: suspending the execution of an old program, mapping the execution state from the old program to a new one, and resuming execution of the new program with the mapped state. The semantic correctness of DSU depends largely on the state mapping which is mostly composed by developers manually nowadays. However, the manual construction of a state mapping does not necessarily ensure sound and dependable state mapping. This dissertation presents a methodology to assist developers by automating the construction of a partial state mapping with a guarantee of correctness. This dissertation includes a detailed study of DSU correctness and automatic state mapping for server programs with an established user base. At first, the dissertation presents the formal treatment of DSU correctness and the state mapping problem. Then the dissertation presents an argument that for programs with an established user base, dynamic updates must be backward compatible. The dissertation next presents a general definition of backward compatibility that specifies the allowed changes in program interaction between an old version and a new version and identified patterns of code evolution that results in backward compatible behavior. Thereafter the dissertation presents formal definitions of these patterns together with proof that any changes to programs in these patterns will result in backward compatible update. To show the applicability of the results, the dissertation presents SitBack, a program analysis tool that has an old version program and a new one as input and computes a partial state mapping under the assumption that the new version is backward compatible with the old version. SitBack does not handle all kinds of changes and it reports to the user in incomplete part of a state mapping. The dissertation presents a detailed evaluation of SitBack which shows that the methodology of automatic state mapping is promising in deal with real world program updates. For example, SitBack produces state mappings for 17-75% of the changed functions. Furthermore, SitBack generates automatic state mapping that leads to successful DSU. In conclusion, the study presented in this dissertation does assist developers in developing state mappings for DSU by automating the construction of state mappings with a correctness guarantee, which helps the adoption of DSU ultimately. / Dissertation/Thesis / Doctoral Dissertation Computer Science 2015
3

Cloneless: Code Clone Detection via Program Dependence Graphs with Relaxed Constraints

Simko, Thomas J 01 June 2019 (has links) (PDF)
Code clones are pieces of code that have the same functionality. While some clones may structurally match one another, others may look drastically different. The inclusion of code clones clutters a code base, leading to increased costs through maintenance. Duplicate code is introduced through a variety of means, such as copy-pasting, code generated by tools, or developers unintentionally writing similar pieces of code. While manual clone identification may be more accurate than automated detection, it is infeasible due to the extensive size of many code bases. Software code clone detection methods have differing degree of success based on the analysis performed. This thesis outlines a method of detecting clones using a program dependence graph and subgraph isomorphism to identify similar subgraphs, ultimately illuminating clones. The project imposes few constraints when comparing code segments to potentially reveal more clones.
4

A Static Slicing Tool for Sequential Java Programs

Devaraj, Arvind January 2007 (has links) (PDF)
A program slice consists of a subset of the statements of a program that can potentially affect values computed at some point of interest. Such a point of interest along with a set of variables is called a slicing criterion. Slicing tools are useful for several applications, such as program understanding, testing, program integration, and so forth. Slicing object oriented programs has some special problems that need to be addressed due to features like inheritance, polymorphism and dynamic binding. Alias analysis is important for precision of slices. In this thesis we implement a slicing tool for sequential Java programs in the Soot framework. Soot is a front-end for Java developed at McGill University and it provides several forms of intermediate code. We have integrated the slicer into the framework. We also propose an improved technique for intraprocedural points-to analysis. We have implemented this technique and compare the results of the analysis with those for a flow-insensitive scheme in Soot. Performance results of the slicer are reported for several benchmarks.

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