42 research outputs found

    Studying the lives of software bugs

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    For as long as people have made software, they have made mistakes in that software. Software bugs are widespread, and the maintenance required to fix them has a major impact on the cost of software and how developers' time is spent. Reducing this maintenance time would lower the cost of software and allow for developers to spend more time on new features, improving the software for end-users. Bugs are hugely diverse and have a complex life cycle. This makes them difficult to study, and research is often carried out on synthetic bugs or toy programs. However, a better understanding of the bug life cycle would greatly aid in developing tools to reduce the time spent on maintenance. This thesis will study the life cycle of bugs, and develop such an understanding. Overall, this thesis examines over 3000 real bugs, from real projects, concentrating on three of the most important points in the life cycle: origin, reporting and fix. Firstly, two existing techniques are compared for discovering the origin of a bug. A number of improvements are evaluated, and the most effective approach is found to be combining the techniques. Furthermore, the behaviour of developers is found to have a major impact on the accuracy of the techniques. Secondly, a large number of bugs are analysed to determine what information is provided when users report bugs. For most bugs, much important information is missing, or inaccurate. Most importantly, there appears to be a considerable gap between what users provide and what developers actually want. Finally, an evaluation is carried out on a number of novel alterations to techniques used to determine the location of bug fixes. Compared to existing techniques, these alterations successfully increase the number of bugs which can be usefully localised, aiding developers in removing the bugs.For as long as people have made software, they have made mistakes in that software. Software bugs are widespread, and the maintenance required to fix them has a major impact on the cost of software and how developers' time is spent. Reducing this maintenance time would lower the cost of software and allow for developers to spend more time on new features, improving the software for end-users. Bugs are hugely diverse and have a complex life cycle. This makes them difficult to study, and research is often carried out on synthetic bugs or toy programs. However, a better understanding of the bug life cycle would greatly aid in developing tools to reduce the time spent on maintenance. This thesis will study the life cycle of bugs, and develop such an understanding. Overall, this thesis examines over 3000 real bugs, from real projects, concentrating on three of the most important points in the life cycle: origin, reporting and fix. Firstly, two existing techniques are compared for discovering the origin of a bug. A number of improvements are evaluated, and the most effective approach is found to be combining the techniques. Furthermore, the behaviour of developers is found to have a major impact on the accuracy of the techniques. Secondly, a large number of bugs are analysed to determine what information is provided when users report bugs. For most bugs, much important information is missing, or inaccurate. Most importantly, there appears to be a considerable gap between what users provide and what developers actually want. Finally, an evaluation is carried out on a number of novel alterations to techniques used to determine the location of bug fixes. Compared to existing techniques, these alterations successfully increase the number of bugs which can be usefully localised, aiding developers in removing the bugs

    Program crash analysis : evaluation and application of current methods

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    After decades of development in computer science, memory corruption bugs still pose a threat to the reliability of software. Automatic crash reporting and fuzz testing are effective ways of gathering information about program bugs. However, these methods can potentially produce thousands of crash dumps, motivating the need for grouping and prioritizing crashes. In addition, the time necessary to analyze the root cause of crashes and to implement a reliable fix in source code should be reduced. This thesis demonstrates how fuzzing can produce a large set of different crashes in a real program. An empirical study explores methods for analyzing these crashes. Automatic bucketing and classification is performed. Call stack based grouping algorithms are compared, and modifications are suggested. Taint analysis is demonstrated as a complementary method to automatic classification based on crash dumps. Dynamic analysis using execution traces is demonstrated as a method for root cause analysis. The empirical study suggests some general results regarding program crash analysis. Crashes should be grouped based on related crash locations and identified similarities in call stacks. A distance algorithm can be used for call stack based grouping and to identify relations between groups. It is suggested that a weighted priority model should be used for prioritizing crashes based on a strategic policy. Some possible metrics are frequency, reliability, severity estimate and relations to already fixed bugs. In order to properly fix a memory corruption bug, the underlying cause should be understood at machine-level. Execution traces with logged operands, differential debugging, Crash Graphs and input analysis might help developers analyze different aspects of memory corruption bugs

    Supporting Source Code Search with Context-Aware and Semantics-Driven Query Reformulation

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    Software bugs and failures cost trillions of dollars every year, and could even lead to deadly accidents (e.g., Therac-25 accident). During maintenance, software developers fix numerous bugs and implement hundreds of new features by making necessary changes to the existing software code. Once an issue report (e.g., bug report, change request) is assigned to a developer, she chooses a few important keywords from the report as a search query, and then attempts to find out the exact locations in the software code that need to be either repaired or enhanced. As a part of this maintenance, developers also often select ad hoc queries on the fly, and attempt to locate the reusable code from the Internet that could assist them either in bug fixing or in feature implementation. Unfortunately, even the experienced developers often fail to construct the right search queries. Even if the developers come up with a few ad hoc queries, most of them require frequent modifications which cost significant development time and efforts. Thus, construction of an appropriate query for localizing the software bugs, programming concepts or even the reusable code is a major challenge. In this thesis, we overcome this query construction challenge with six studies, and develop a novel, effective code search solution (BugDoctor) that assists the developers in localizing the software code of interest (e.g., bugs, concepts and reusable code) during software maintenance. In particular, we reformulate a given search query (1) by designing novel keyword selection algorithms (e.g., CodeRank) that outperform the traditional alternatives (e.g., TF-IDF), (2) by leveraging the bug report quality paradigm and source document structures which were previously overlooked and (3) by exploiting the crowd knowledge and word semantics derived from Stack Overflow Q&A site, which were previously untapped. Our experiment using 5000+ search queries (bug reports, change requests, and ad hoc queries) suggests that our proposed approach can improve the given queries significantly through automated query reformulations. Comparison with 10+ existing studies on bug localization, concept location and Internet-scale code search suggests that our approach can outperform the state-of-the-art approaches with a significant margin

    Root cause prediction based on bug reports

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    This paper proposes a supervised machine learning approach for predicting the root cause of a given bug report. Knowing the root cause of a bug can help developers in the debugging process - either directly or indirectly by choosing proper tool support for the debugging task. We mined 54755 closed bug reports from the issue trackers of 103 GitHub projects and applied a set of heuristics to create a benchmark consisting of 10459 reports. A subset was manually classified into three groups (semantic, memory, and concurrency) based on the bugs' root causes. Since the types of root cause are not equally distributed, a combination of keyword search and random selection was applied. Our data set for the machine learning approach consists of 369 bug reports (122 concurrency, 121 memory, and 126 semantic bugs). The bug reports are used as input to a natural language processing algorithm. We evaluated the performance of several classifiers for predicting the root causes for the given bug reports. Linear Support Vector machines achieved the highest mean precision (0.74) and recall (0.72) scores. The created bug data set and classification are publicly available.Comment: 6 page

    PerfBlower: Quickly Detecting Memory-Related Performance Problems via Amplification

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    Performance problems in managed languages are extremely difficult to find. Despite many efforts to find those problems, most existing work focuses on how to debug a user-provided test execution in which performance problems already manifest. It remains largely unknown how to effectively find performance bugs before software release. As a result, performance bugs often escape to production runs, hurting software reliability and user experience. This paper describes PerfBlower, a general performance testing framework that allows developers to quickly test Java programs to find memory-related performance problems. PerfBlower provides (1) a novel specification language ISL to describe a general class of performance problems that have observable symptoms; (2) an automated test oracle via emph{virtual amplification}; and (3) precise reference-path-based diagnostic information via object mirroring. Using this framework, we have amplified three different types of problems. Our experimental results demonstrate that (1) ISL is expressive enough to describe various memory-related performance problems; (2) PerfBlower successfully distinguishes executions with and without problems; 8 unknown problems are quickly discovered under small workloads; and (3) PerfBlower outperforms existing detectors and does not miss any bugs studied before in the literature

    Security and Privacy in Bluetooth Low Energy

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    Statistical debugging for real-world performance problems

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