Locating bugs without looking back

Bug localisation is a core program comprehension task in software maintenance: given the observation of a bug, e.g. via a bug report, where is it located in the source code? Information retrieval (IR) approaches see the bug report as the query, and the source code files as the documents to be retrieved, ranked by relevance. Such approaches have the advantage of not requiring expensive static or dynamic analysis of the code. However, current state-of-the-art IR approaches rely on project history, in particular previously fixed bugs or previous versions of the source code. We present a novel approach that directly scores each current file against the given report, thus not requiring past code and reports. The scoring method is based on heuristics identified through manual inspection of a small sample of bug reports. We compare our approach to eight others, using their own five metrics on their own six open source projects. Out of 30 performance indicators, we improve 27 and equal 2. Over the projects analysed, on average we find one or more affected files in the top 10 ranked files for 76% of the bug reports. These results show the applicability of our approach to software projects without history

Utilizing traceable software artifacts to improve bug localization

Die Entwicklung von Softwaresystemen ist eine komplexe Aufgabe. Qualitätssicherung versucht auftretenden Softwarefehler (bugs) in Systemen zu vermeiden, jedoch können Fehler nie ausgeschlossen werden. Sobald ein Softwarefehler entdeckt wird, wird typischerweise ein Fehlerbericht (bug report) erstellt. Dieser dient als Ausgangspunkt für den Entwickler den Fehler im Quellcode der Software zu finden und zu beheben (bug fixing). Fehlerberichte sowie weitere Softwareartefakte, z.B. Anforderungen und der Quellcode selbst, werden in Software Repositories abgelegt. Diese erlauben die Artefakte mit trace links zur Nachvollziehbarkeit (traceability) zu verknüpfen. Oftmals ist die Erstellung der trace links im Entwicklungsprozess vorgeschrieben. Dazu zählen u.a. die Luftfahrt- und Automobilindustrie, sowie die Entwicklung von medizinischen Geräten. Das Auffinden von Softwarefehlern in großen Systemen mit tausenden Artefakten ist eine anspruchsvolle, zeitintensive und fehleranfällige Aufgabe, welche eine umfangreiche Projektkenntnis erfordert. Deswegen wird seit Jahren aktiv an der Automatisierung dieses Prozesses geforscht. Weiterhin wird die manuelle Erstellung und Pflege von trace links als Belastung empfunden und sollte weitgehend automatisiert werden. In dieser Arbeit wird ein neuartiger Algorithmus zum Auffinden von Softwarefehlern vorgestellt, der aktiv die erstellten trace links ausnutzt. Die Artefakte und deren Beziehungen dienen zur Erstellung eines Nachvollziehbarkeitsgraphen, welcher analysiert wird um fehlerhafte Quellcodedateien anhand eines Fehlerberichtes zu finden. Jedoch muss angenommen werden, dass nicht alle notwendigen trace links zwischen den Softwareartefakten eines Projektes erstellt wurden. Deswegen wird ein vollautomatisierter, projektunabhängiger Ansatz vorgestellt, der diese fehlenden trace links erstellt (augmentation). Die Grundlage zur Entwicklung dieses Algorithmus ist der typische Entwicklungsprozess eines Softwareprojektes. Die entwickelten Ansätze wurden mit mehr als 32.000 Fehlerberichten von 27 Open-Source Projekten evaluiert und die Ergebnisse zeigen, dass die Einbeziehung von traceability signifikant das Auffinden von Fehlern im Quellcode verbessert. Weiterhin kann der entwickelte Augmentation Algorithmus zuverlässig fehlende trace links erstellen.The development of software systems is a very complex task. Quality assurance tries to prevent defects – software bugs – in deployed systems, but it is impossible to avoid bugs all together, especially during development. Once a bug is observed, typically a bug report is written. It guides the responsible developer to locate the bug in the project's source code, and once found to fix it. The bug reports, along with other development artifacts such as requirements and the source code are stored in software repositories. The repositories also allow to create relationships – trace links – among contained artifacts. Establishing this traceability is demanded in many domains, such as safety related ones like the automotive and aviation industry, or in development of medical devices. However, in large software systems with thousands of artifacts, especially source code files, manually locating a bug is time consuming, error-prone, and requires extensive knowledge of the project. Thus, automating the bug localization process is actively researched since many years. Further, manually creating and maintaining trace links is often considered as a burden, and there is the need to automate this task as well. Multiple studies have shown, that traceability is beneficial for many software development tasks. This thesis presents a novel bug localization algorithm utilizing traceability. The project's artifacts and trace links are used to create a traceability graph. This graph is then analyzed to locate defective source code files for a given bug report. Since the existing trace link set of a project is possibly incomplete, another algorithm is prosed to augment missing links. The algorithm is fully automated, project independent, and derived from a project's development workflow. An evaluation on more than 32,000 bug reports from 27 open-source projects shows, that incorporating traceability information into bug localization significantly improves the bug localization performance compared to two state of the art algorithms. Further, the trace link augmentation approach reliably constructs missing links and therefore simplifies the required trace maintenance

Locating Bugs without Looking Back

Bug localisation is a core program comprehension task in software maintenance: given the observation of a bug, where is it located in the source code files? Information retrieval (IR) approaches see a bug report as the query, and the source code files as the documents to be retrieved, ranked by relevance. Such approaches have the advantage of not requiring expensive static or dynamic analysis of the code. However, most of state-of-the-art IR approaches rely on project history, in particular previously fixed bugs and previous versions of the source code. We present a novel approach that directly scores each current file against the given report, thus not requiring past code and reports. The scoring is based on heuristics identified through manual inspection of a small set of bug reports. We compare our approach to five others, using their own five metrics on their own six open source projects. Out of 30 performance indicators, we improve 28. For example, on average we find one or more affected files in the top 10 ranked files for 77% of the bug reports. These results show the applicability of our approach to software projects without history

Leveraging Identifier Naming Structures in Source Code and Bug Reports to Localize Relevant Bugs

When bugs are found in source code, bug reports are created which contain relevant information for developers to locate and fix the bug. In large source code repositories, it can be difficult and time consuming for developers to manually analyze bug reports to locate a bug. The discovery of patterns between bug reports and source files has led to the creation of automated tools using various techniques. Automated bug localization techniques can reduce the amount of manual effort required by developers by ranking the most probable location of the bug using textual information from bug reports and source code. Although these approaches offer some assistance, the lexical mismatch between the bug reports and the source code makes it difficult to accurately locate the buggy source code file(s) using Information Retrieval (IR) techniques. Our research proposes a technique that takes advantage of the lexical and structural patterns observed in source code identifier names to help offset the mismatch between bug reports and their related source code files. Our observations reveal that there are lexical and structural identifier naming trends for different identifier types in the source code. Using two open-source projects, and collecting frequencies for observed identifier patterns across the project, we applied the observed frequencies to matched word occurrences in bug reports across our evaluation data set to modify the significance of that word. Based on observations discovered in our empirical analysis of open source repositories ElasticSearch and RxJava, we developed a method to modify the significance of a word by altering the weight of the matched word represented in the Term Frequency - Inverse Document Frequency (TF-IDF) vectorization of that particular bug report. The idea behind this approach is that if we come across a word perceived to be significant based on our observed identifier pattern frequency data, we can apply a weight to that word in the bug report vectorization to increase the cosine similarity score between the bug report and source file vectors. This work expands and improves upon previous work by Gharibi et al. [1], who propose a multicomponent approach that uses token matching, stack trace, semantic similarity, and a revised vector space model (rVSM). Specifically, our approach modifies the rVSM component, and our work is evaluated on the same three open-source software projects: AspectJ, SWT, and ZXing. The results of our approach are comparable to the results of Gharibi et al., and we achieve an improvement in some cases. It was observed that our work outperforms many existing bug localization approaches. Top@N, Mean Reciprocal Rank (MRR), and Mean Average Precision (MAP) are metrics used to evaluate and rank our work against other approaches, revealing some improvement in bug localization across three open-source projects

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

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

Efficient Information Retrieval for Software Bug Localization

Software systems are often shipped with defects. When a bug is reported, developers use the information available in the associated report to locate source code fragments that need to be modified to fix the bug. However, as software systems evolve in size and complexity, bug localization can become a tedious and time-consuming process. Contemporary bug localization tools utilize Information Retrieval (IR) methods for automated support to minimize the manual effort. IR methods exploit the textual content of bug reports to capture and rank relevant buggy source files. However, for an IR-based bug localization tool to be useful, it must achieve adequate retrieval accuracy. Lower precision and recall can leave developers with large amounts of incorrect information to wade through. Motivated by these observations, in this dissertation, we propose a new paradigm of information-theoretic IR methods to support bug localization tasks in software systems. These methods exploit the co-occurrence patterns of code terms in software systems to reveal latent semantic information that other methods often fail to capture. We further investigate the impact of combining various IR methods on the retrieval accuracy of bug localization engines. The main assumption is that different IR methods, targeting different dimensions of similarity between software artifacts, can enhance the confidence in each other\u27s results. Furthermore, we propose a novel approach for enhancing the performance of IR-enabled bug localization methods in the context of Open-Source Software (OSS). The proposed approach exploits knowledge from previously resolved bugs to help localize new bugs. Our analysis uses multiple datasets generated for multiple open-source and closed source projects. Our results show that a) information-theoretic IR methods can significantly outperform classical IR methods in bug localization tasks, b) optimized IR-hybrids can significantly outperform individual IR methods, and near-optimal global configurations can be determined for different combinations of IR methods, and c) information extracted from previously resolved bug reports can significantly enhance the accuracy of IR-enabled bug localization methods in OSS

Effective bug detection and localization using information retrieval

Software bugs pose a fundamental threat to the reliability of software systems, even in systems designed with the best software engineering (SE) teams using the best SE practices. Detecting bugs early and fixing them quickly are extremely important. However, they are very expensive and challenging, especially at-scale. While the sciences of bug detection (e.g., software testing) and localization via static and dynamic program analyses have been explored considerably, text-based Information Retrieval (IR) techniques for bug detection and localization are interesting and promising new approaches for these problems. One advantage of text-based approaches is that it can utilize a lot of (implicit) semantic information about a program’s functionality from the program text, which is almost impossible to extract using program analysis based techniques. This dissertation builds a deeper understanding of current bug triaging and fixing processes via mining software repositories, and introduces new techniques for effective bug detection and localization. The dissertation has three main parts. First, we perform a number of empirical studies to investigate the extent of and reasons for long lived bugs, their severities, and time spent in different phases of bug fixing process. We demonstrate that many bugs remain unfixed for inordinate period of time due to numerous reasons, including difficulties in detecting, localizing, and fixing them. Second, we demonstrate that developers use very similar program text in source code and their corresponding test cases, which could be utilized to implement powerful test prioritization techniques. We introduce a novel IR based regression test prioritization technique called REPiR that embodies our insight, and show that REPiR is more efficient than program analysis based or dynamic coverage based techniques. Third, we demonstrate that fine grained program text such as class names, method names, variable names, and comments carry different levels of information, and it can be utilized to improve IR based bug localization. We introduce a structured retrieval technique called BLUiR that embodies our insights and show that BLUiR outperforms the existing state-of-the-art IR-based bug localization approaches. Finally, we further improve BLUiR by natural language processing. We make four contributions in this dissertation. One, we provide empirical evidence that there are considerable numbers of non-trivial bugs in software projects that survive for a long time. We describe the reasons for delay in fixing, the nature of fixes, and overall fixing process of these long lived bugs in a great detail. Two, we introduce the notion of IR-based regression test prioritization based on program changes. Three, we introduce the notion of structured retrieval for bug localization. Four, we provide an in-depth analysis of the extent to which natural languages processing can play an important role in improving IR-based bug localization further. The central ideas are embodied in a suite of prototype tools. Rigorous empirical evaluation is performed to validate the efficacy of the proposed techniques using datasets containing a variety of real-world Java and C programs.Electrical and Computer Engineerin

Improving Information Retrieval Bug Localisation Using Contextual Heuristics

Software developers working on unfamiliar systems are challenged to identify where and how high-level concepts are implemented in the source code prior to performing maintenance tasks. Bug localisation is a core program comprehension activity in software maintenance: given the observation of a bug, e.g. via a bug report, where is it located in the source code? Information retrieval (IR) approaches see the bug report as the query, and the source files as the documents to be retrieved, ranked by relevance. Current approaches rely on project history, in particular previously fixed bugs and versions of the source code. Existing IR techniques fall short of providing adequate solutions in finding all the source code files relevant for a bug. Without additional help, bug localisation can become a tedious, time- consuming and error-prone task. My research contributes a novel algorithm that, given a bug report and the application’s source files, uses a combination of lexical and structural information to suggest, in a ranked order, files that may have to be changed to resolve the reported bug without requiring past code and similar reports. I study eight applications for which I had access to the user guide, the source code, and some bug reports. I compare the relative importance and the occurrence of the domain concepts in the project artefacts and measure the effectiveness of using only concept key words to locate files relevant for a bug compared to using all the words of a bug report. Measuring my approach against six others, using their five metrics and eight projects, I position an effected file in the top-1, top-5 and top-10 ranks on average for 44%, 69% and 76% of the bug reports respectively. This is an improvement of 23%, 16% and 11% respectively over the best performing current state-of-the-art tool. Finally, I evaluate my algorithm with a range of industrial applications in user studies, and found that it is superior to simple string search, as often performed by developers. These results show the applicability of my approach to software projects without history and offers a simpler light-weight solution

Duplicate Defect Detection

Discovering and fixing faults is an unavoidable process in Software Engineering. It is always a good practice to document and organize fault reports. This facilitates the effectiveness of development and maintenance process. Bug Tracking Repositories, such as Bugzilla, are designed to provide fault reporting facilities for developers, testers and users of the system. Allowing anyone to contribute finding and reporting faults has an immediate impact on software quality. However, this benefit comes with one side-effect. Users often file reports that describe the same fault. This increases the triaging time spent by the maintainers. At the same time, important information required to fix the fault is likely to be distributed across different reports.;The objective of this thesis is twofold. First, we want to understand the dynamics of bug report filing for a large, long duration open source project, Firefox. Second, we present a new approach that can reduce the number of duplicate reports. The novel element in the proposed approach is the ability to concentrate the search for duplicates on specific portions of the bug repository. This improves the performance of Information Retrieval techniques and classification runtime of our algorithm. Our system can be deployed as a search tool to help reporters query the repository or it can be adopted to help maintainers detect duplicate reports. In both cases the performance is satisfactory. When tested as a search tool our system is able to detect up to 53% of duplicate reports. The approach adapted for maintainers has a maximum recall rate of 59%