Fixing bugs in hardware design code has become a challenging task due to the increasing complexity of modern circuit designs. As a result, automated program repair techniques have been proposed to synthesize patches for bugs in hardware designs and achieved promising results. However, existing techniques are still limited in synthesizing expressions for complex bugs. In this work, we explore the possibility of addressing complex bugs by proposing SREPAIR, a novel symbolic regression-based repair technique. The key novelty of SREPAIR lies in three aspects: 1) we propose a novel expression modification encoding that enables fine-grained adjustments to buggy expressions. 2) we introduce expression synthesis-based templates that allow for flexible and expressive repairs. 3) we develop a novel symbolic regression network-based synthesis algorithm that effectively synthesizes complex expressions. Experimental results on the four peer-reviewed datasets demonstrate that SREPAIR correctly fixes 56 bugs out of 112 bugs, which achieves 43.6% and 194.7% improvement over the previous state-of-the-art RTL-REPAIR (39 bugs) and CIRFIX (19 bugs). To evaluate the generalizability of SREPAIR, we further construct an augmented dataset of 282 bugs by mutating hardware designs. SREPAIR shows its better generalizability by correctly fixing 127 bugs, reaching 217.5% improvement over the best approach.

The software development process is characterized by an iterative cycle of continuous functionality implementation and debugging, essential for the enhancement of software quality and adaptability to changing requirements. This process incorporates two isolatedly studied tasks: Code Search (CS), which retrieves reference code from a code corpus to aid in code implementation, and Fault Localization (FL), which identifies code entities responsible for bugs within the software project to boost software debugging. The basic observation of this study is that these two tasks exhibit similarities since they both address search problems. Notably, CS techniques have demonstrated greater effectiveness than FL ones, possibly because of the precise semantic details of the required code offered by natural language queries, which are not readily accessible to FL methods. Drawing inspiration from this, we hypothesize that a fault localizer could achieve greater proficiency if semantic information about the buggy methods were made available. Based on this idea, we propose \(\texttt{CosFL}\) , an FL approach that decomposes the FL task into two steps: query generation , which describes the functionality of the problematic code in natural language, and fault retrieval , which uses CS to find program elements semantically related to the query, allowing for finishing the FL task from a CS perspective. Specifically, to depict the buggy functionalities and generate high-quality queries, \(\texttt{CosFL}\) extensively harnesses the code analysis, semantic comprehension, text generation, and decision-making capabilities of LLMs. Moreover, to enhance the accuracy of CS, \(\texttt{CosFL}\) captures varying levels of context information and employs a multi-granularity CS strategy, which facilitates a more precise identification of buggy methods from a holistic view. The evaluation on 835 real bugs from 23 Java projects shows that \(\texttt{CosFL}\) successfully localizes 324 bugs within Top-1, which significantly outperforms the state-of-the-art approaches by 26.6%–57.3%. The ablation study and sensitivity analysis further validate the importance of different components and the robustness of \(\texttt{CosFL}\) across different backend models.

The growing prominence of deep code models in automating software engineering tasks is undeniable. However, their deployment encounters significant challenges in on-the-fly performance enhancement , which refers to dynamically improving the performance of deep code models during real-time execution. Conventional techniques, such as retraining or fine-tuning, are effective in controlled pre-deployment scenarios but fall short when adapting to on-the-fly adjustments post-deployment. CodeDenoise, a notable on-the-fly performance enhancement technology, leverages uncertainty-based methods to identify misclassified inputs and applies an input modification strategy to rectify classification errors. While effective for classification tasks, this approach is inapplicable to generative tasks due to two key challenges: ❶ Uncertainty-based methods are unsuitable for identifying challenging inputs , especially in generative tasks with diverse and open-ended outputs. Challenging inputs refers to a class of inputs where, due to the inherent complexity of the task or insufficient context in the input samples, the model struggles to generate high-quality outputs. ❷ Input modification strategies cannot be applied to generative tasks, as modifying the input can unpredictably affect the entire sequence of generated outputs. These limitations highlight the need for novel techniques that can enhance the generation quality of deep code models in real-time. To bridge this gap, we propose CodEn , a framework designed to enhance the generation quality of deployed deep code models through model collaboration and real-time output repair. CodEn employs an ensemble learning approach, integrating multiple generic output quality assessment metrics to identify challenging inputs . By combining these diverse metrics, CodEn overcomes the limitations of uncertainty-based methods, making it effective across various generative tasks. Additionally, we introduce an elaborate on-the-fly repair method for the outputs of challenging inputs , leveraging a Large Language Model (LLM) and a novel dual-prompt strategy. This strategy utilizes both generation and selection-based prompts to provide potential fixes and employs an adaptive mechanism to select the optimal output. Our experiments, conducted on 12 deep code models across three pre-trained code models, three popular code-related generation tasks, and four datasets, demonstrate the effectiveness of CodEn . For example, in the assertion generation task, CodEn enhances the Semantic Accuracy Match (SAM) of baseline models with improvements ranging from 12.14% to 21.65%. In the bug fixing task, CodEn achieves exact match gains ranging from 17.51% to 30.64% on TFix dataset. For the code summarization task, CodEn significantly boosts performance across key metrics: BLEU scores improved by 5.72%–11.79%, ROUGE-L by 4.41%–7.70%, METEOR by 7.51%–12.29%, and CIDEr by 8.09%–15.80%. Besides, we conduct experiments of CodEn on different open source LLMs and demonstrate that CodEn can still achieve significant improvements.

Coincidental Correctness (CC) arises when a test case executes faulty entity in a program without causing a failure. This phenomenon injects noise into coverage information, as CC tests weaken the connection between faulty entities and test failures. Since many fault localization (FL) approaches relies on analyzing test execution traces to locate faulty entities, the compromised reliability of test results directly undermines FL accuracy. Furthermore, the detrimental effects of CC extend beyond fault localization to subsequent software maintenance tasks like automatic program repair. Therefore, identifying and mitigating CC tests becomes critical not only for enhancing FL but also for ensuring robust software quality assurance. Thus, we propose FusionCC: an approach that applies multiscale coverage features and handcrafted features to fuse complementary feature representations for CC test case detection. Specifically, FusionCC first refines original coverage data by filtering out noisy irrelevant elements, then extracts multiscale features from the refined matrix, and finally fuses the coverage and handcrafted features to generate highly informative feature representations for CC detection. FusionCC realizes a comprehensive fusion of complementary features across different scales and from diverse sources, which significantly enhances the accuracy of CC detection. To evaluate the effectiveness of FusionCC, we conduct large-scale experiments on 277 faulty versions of six representative benchmarks. The experimental results show that FusionCC significantly improves CC detection (e.g., average improvements of 50.93% precision and 82.03% in$F_{1}$value compared to state-of-the-art CC detection approaches) and fault localization effectiveness (e.g., 10.33, 19.33, 25.67 average faults can be found in terms of Top-1, Top-3, Top-5 metrics at relabel strategy compared with state-of-the-art FL approaches).

As deep learning (DL) systems are increasingly deployed in safety-critical domains, e.g., intelligent planning and autonomous driving, localizing faults that occur in such systems becomes indispensable. Inevitably, DL systems also suffer from faults like traditional software. Although single fault localization for DL programs has been studied, the multiple-fault localization for DL programs remains underexplored. We notice that mutation analysis is a powerful technique for locating multiple faults since it can simulate the faulty behaviors of a DL program by generating multiple mutants simultaneously. Thus, we propose MuMuFL: StatisticalMutation-basedMultipleFaultLocalization approach to locate the multiple faulty statements residing in a faulty DL program. The insight of MuMuFL is that the different behaviors of mutants provide valuable information for pinpointing the faulty statements of a DL fault. MuMuFL defines and leverages DL mutation operators on a DL program to simulate the faulty DL behavior. Then, MuMuFL evaluates the difference in the accuracy between the original DL model and the mutated DL model to quantify the suspiciousness of each statement being faulty. Finally, the large-scale experiments show that MuMuFL effectively localizes DL faults, e.g., localizing 36% of multiple-fault DL programs, whereas the best-performing baseline can only localize 14% of them.

Test Case Prioritization (TCP) is a critical technique for improving efficiency in CI/CD pipelines. While applying Large Language Models (LLMs) to this task is a promising direction due to their advanced code comprehension, naively using them as monolithic tools fails to address key engineering challenges of scale, tool-integration, and structured reasoning. To address these shortcomings, we propose AgentTCP, a novel collaborative multi-agent framework for change-aware test case prioritization. Our framework decomposes the TCP task into a structured, three-stage workflow managed by specialized, LLM-driven agents: 1) a Code Change Analyst assesses the intent and risk of new commits; 2) a Test Coverage Strategist correlates changes with test cases by interacting with coverage data via tool-integration; 3) a Risk-aware Prioritizer synthesizes all information to generate a final, ranked list with reasoning. By delegating distinct responsibilities, AgentTCP mitigates the context and reasoning issues of monolithic models and produces verifiable intermediate results, enhancing overall trustworthiness. Experimental results on the widely used Defects4J benchmark demonstrate that AgentTCP surpasses the monolithic-LLM baseline by 11.75 points in terms of the APFD metric, highlighting its superior effectiveness in prioritizing fault-revealing test cases.

Fault localization (FL) can identify the fault's location by analyzing the execution information from test cases in the program. This execution information serves as the foundation for FL to infer latent causal relationships between fault entities and failed results. However, this execution information contains coincidental correctness (CC), which reduces the accuracy of FL. CC arises when a test case executes faulty program entities but still produces the correct output, leading to misleading FL inferences. In widely used datasets, the presence of CC compromises the reliability of passed test cases (i.e., negative labels). In contrast, failed test cases (i.e., positive labels) remain definitive. In FL scenarios, unlabeled data is typically abundant and primarily consists of passed test cases. Therefore, systematically leveraging positive and unlabeled data for accurate CC detection is essential, which is beneficial to FL. To tackle the problem, we propose a two-stagE positiVe and unlAbeled learning model for coiNcidental correctneSs detection, EVANS. EVANS defines failed test cases as positive samples and treats the remaining ones as unlabeled data. It comprises two core modules: (1) A module for selecting high-quality pseudo-negative samples. This module leverages vector distance metrics to identify high-quality pseudo-negative test cases, using inter-class distances computed via a pre-trained model. (2) A weakly supervised contrastive learning module. This module utilizes the labeled samples from Stage (1) to train a contrastive learning model, which then detects CC in unlabeled test cases. Experimental results demonstrate that EVANS significantly outperforms current CC detection methods.

Coincidental correctness (CC) refers to test cases that execute faulty code but still produce excepted outputs. This phenomenon introduces noise into the data of software testing-related tasks. As demonstrated in the literature, CC has negative impact on test suite reduction, test case prioritization, fault localization, and automated program repair. Thus, it is essential to detect and mitigate the impact of CC. Although CC is commonly observed across a large number of programs, CC test cases are typically sparse within each program’s test suite. In other words, CC test cases generally make up merely a small portion of the passing test cases. The proportions vary from 3.27% to 31.74% within Defects4J V1.4. This results in a highly imbalanced distribution of CC versus non-CC test cases, posing challenges for accurate detection.To address this issue, we propose a Diffusion-Enhanced and Feature-Aligned Framework for Coincidental Correctness detection, named DEFACC, to obtain more structured representations of test cases. Specifically, DEFACC first introduces a diffusion-based generation module. This module generates new CC samples from original samples to alleviate class imbalance issue and enhance the diversity of CC samples. However, generated feature samples may deviate from the distribution of real CC samples. Such shifts can hurt model reliability and generalization. To resolve this, DEFACC integrates a feature alignment module that is founded on the Maximum Mean Discrepancy (MMD) loss. This module enforces distributional consistency between generated and original CC samples during training. Together, these components ensure that the augmented samples are from sparse to structured, which is not only quantitatively balanced but also semantically faithful. Experimental results show that the DEFACC significantly improves the performance of existing CC detection methods and provides a stronger representation foundation for accurate fault localization.

In recent years, significant progress has been made in testing methods for deep neural networks (DNNs) to ensure their correctness and robustness. Coverage-guided criteria, such as neuron-wise, layer-wise, and path-/trace-wise, have been proposed for DNN fuzzing. However, existing coverage-based criteria encounter performance bottlenecks for several reasons: ❶ Testing Adequacy : Partial neural coverage criteria have been observed to achieve full coverage using only a small number of test inputs. In this case, increasing the number of test inputs does not consistently improve the quality of models. ❷ Interpretability : The current coverage criteria lack interpretability. Consequently, testers are unable to identify and understand which incorrect attributes or patterns of the model are triggered by the test inputs. This lack of interpretability hampers the subsequent debugging and fixing process. Therefore, there is an urgent need for a novel fuzzing criterion that offers improved testing adequacy, better interpretability, and more effective failure detection capabilities for DNNs. To alleviate these limitations, we propose NSGen, an approach for DNN fuzzing that utilizes neuron semantics as guidance during test generation. NSGen identifies critical neurons, translates their high-level semantic features into natural language descriptions, and then assembles them into human-readable DNN decision paths (representing the internal decision of the DNN). With these decision paths, we can generate more fault-revealing test inputs by quantifying the similarity between original test inputs and mutated test inputs for fuzzing. We evaluate NSGen on popular DNN models (VGG16_BN, ResNet50, and MobileNet_v2) using CIFAR10, CIFAR100, Oxford 102 Flower, and ImageNet datasets. Compared to 12 existing coverage-guided fuzzing criteria, NSGen outperforms all baselines, increasing the number of triggered faults by 21.4% to 61.2% compared to the state-of-the-art coverage-guided fuzzing criterion. This demonstrates NSGen's effectiveness in generating fault-revealing test inputs through guided input mutation, highlighting its potential to enhance DNN testing and interpretability.

Multiple fault localization (MFL) identifies the positions of multiple faults (i.e., more than one fault) residing in a buggy program. It is notably more difficult as compared with single fault localization (SFL) which aims to locate a single fault (i.e., one fault) in a buggy program. Clustering-based multiple fault localization (CBMFL) is amongst the most popular MFL approaches, showing promising results in multiple fault localization. The requisite of launching CBMFL depends on test oracles to acquire the test results (i.e., a pass or a failure). In practice, test oracles are commonly not available known as the oracle problem, and CBMFL becomes infeasible in these cases. Inspired by metamorphic testing in solving the oracle problem, we attempt to combine this technique into CBMFL to broaden its application scope. Thus, we propose MetaMFL:MetamorphicMultipleFaultLocalization, which leverages metamorphic testing to extend CBMFL to the cases where test oracles are not available. Specifically, MetaMFL uses metamorphic testing groups as minimum units of testing. It defines metamorphic features for representing those that have violated metamorphic relations. Using these features, CBMFL can perform clustering to support parallel debugging, thus achieving MFL without test oracles. The large-scale experiments show that MetaMFL largely retains the effectiveness of CBMFL even though test oracles are not available.

Coincidental correctness (CC) can be misleading for developers because it gives the impression that the code is functioning correctly when there are hidden faults. To mitigate the negative impacts of CC test cases, extensive research has been conducted on their detection, employing either coverage-based or expert-based features. These studies have yielded promising results. Coverage and expert features each provide unique insights into program execution, yet the literature has not fully explored the combined potential of these two feature sets to enhance the detection of CC. Additionally, the rich semantics of the test code and focal method have not been fully utilized. Therefore, we propose to build a unified model, CORE, that integrates coverage and expert features with semantic representations of test and focal methods to improve the detection of CC test cases. We make a comprehensive evaluation with six state-of-the-art baselines on the widely-used Defects4J benchmark. The experimental results show that CORE outperforms the baselines in terms of CC detection accuracy, with a substantial improvement (i.e., 40% improvement on average in terms of F1 score). Then, we conduct the ablation experiment to show that the coverage, expert, and semantics contribute to CORE. CORE can also improve the effectiveness of spectrum-based and mutation-based fault localization performance (e.g., 50% improvements for spectrum-based formula Dstar and 44% improvements for mutation-based method MUSE under relabeling strategy).

The ideal principle of software testing is that test results ought to be deterministic: a test failure indicates the presence of a software bug, while a test success suggests the absence of a bug. Nevertheless, flaky tests break the principle. Flaky tests yield inconsistent results when executed repeatedly under the same conditions. The most straightforward approach runs the tests multiple times to predict flaky tests whereas it is highly time-consuming. Many researchers have proposed efficient approaches to reduce the cost, e.g., recent approaches leverage machine learning techniques for the prediction of flaky tests. However, traditional machine learning primarily focuses on predicting specific instances, which is not conducive to identify flaky tests across an entire project. Therefore, we propose Flakyrank, a ranking framework based on augmented learning to rank to predict flaky tests. The insight is that learning to rank, as compared with traditional machine learning, not only concentrates on individual samples but also optimizes the overall ranking. Since flaky tests constitute a small proportion of the dataset (i.e., approximately 3.6% of the total tests), we utilize generative adversarial networks to generate some synthetic flaky tests to augment the dataset. Based on the augmented dataset, FLAKYRANK treats predicting flaky tests as an information retrieval task, where newly detected flaky tests and test cases serve as queries and documents, respectively. For each newly detected flaky test (i.e., query), FLAKYRANK combines multiple relevant features into a learning to rank model to predict flaky tests candidate tests. We conduct large-scale experiments on different learning to rank models, and the results show that FLAKYRANK with the LambdaMART algorithm yields the best performance. In addition, the experimental results on 23 benchmark projects show that FLAKYRANK outperforms the state-of-the-art predictors.

Manual fixing of compilation errors could be a tedious and time-consuming task for novice programmers, and even for experienced ones. In recent years, an increasing number of automated repair techniques have been proposed to guide novice programmers and improve the efficiency of software development. Among them, learning-based automated repair techniques have achieved promising results in terms of repair accuracy. However, existing approaches neglect the time efficiency of patch generation, and often treat the compilation errors repair as a neural machine translation task. The end-to-end repair model decoding cannot be parallelized during the inference stage and suffers from redundant decoding search space. Furthermore, the large search space brought by the model poses a potential risk of semantic tampering. To this end, we propose Labelrepair, a novel repair technique that treats the repair of compilation errors as a sequence labelling task. Labelrepair discards the decoding model and converts the search for patches to a search for the error mapping actions between broken code and patch code pairs. In this way, the search space for patch tokens is plum-meted from the entire vocabulary to the size of edit action labels, and the logical semantics of the original program are preserved to some extent. The time complexity of inference is reduced from$O(n)$to$O$(1) owing to the parallel generation of edit action labels. Through a comprehensive evaluation of Labelrepair on two datasets, we demonstrate that Labelrepair is able to generate patches instantly (0.71ms on average), which is 28 times faster than existing end-to-end repair models. Compared with existing edit-based repair models, Labelrepair achieves the state-of-art repair accuracy.

Hardware description languages (HDLs) are pivotal for the development of hardware designs. The programming courses for HDLs are also popular in both universities and online course platforms. Similar to programming assignments of software languages (SLs), these of HDLs also actively call for automated program repair (APR) techniques to provide personalized feedback for students. However, the research of APR techniques targeting HDL programming assignments is still in an early stage. Due to the significantly different programming mechanism of HDLs from SLs, the only APR technique (i.e., CirFix) targeting HDL programming assignments contributes a customized repair pipeline. However, the fundamental challenges in the design of HDL-oriented fault localization and patch generation still remain unresolved. In this work, we propose a signal value transition-guided defect repair technique named STRIDER by capturing the intrinsic features of HDLs. This technique consists of a time-aware dynamic defect localization approach to precisely localize defects, and a signal value transition-guided patch synthesis approach to effectively generate fixes.We further construct a dataset of 57 real defects from HDL programming assignments for tool evaluation. The evaluation reveals the overfitting issue of the pioneering tool CirFix and the significant improvement of STRIDER over CirFix in terms of both effectiveness and efficiency. In particular, STRIDER is more effective by correctly fixing 2.3X as many defects as CirFix in the real defect dataset, and is 23X more efficient by generating a correct fix within five minutes on average in the synthetic defect dataset, while CirFix takes around two hours on average.

Test-to-code traceability links (TCTLs) establish links between test artifacts and code artifacts. These links enable developers and testers to quickly identify the specific pieces of code tested by particular test cases, thus facilitating more efficient debugging, regression testing, and maintenance activities. Various approaches, based on distinct concepts, have been proposed to establish method-level TCTLs, specifically linking unit tests to corresponding focal methods. Static methods, such as naming-convention-based methods, use heuristic- and similarity-based strategies. However, such methods face the following challenges: ① Developers, driven by specific scenarios and development requirements, may deviate from naming conventions, leading to TCTL identification failures. ② Static methods often overlook the rich semantics embedded within tests, leading to erroneous associations between tests and semantically unrelated code fragments. Although dynamic methods achieve promising results, they require the project to be compilable and the tests to be executable, limiting their usability. This limitation is significant for downstream tasks requiring massive test-code pairs, as not all projects can meet these requirements. To tackle the abovementioned limitations, we propose a novel static method-level TCTL approach, namedTestLinker. For the first challenge of existing static approaches,TestLinkerintroduces a two-phase TCTL framework to accommodate different project types in a triage manner. As for the second challenge, we employ thesemantic correlation learning, which learns and establishes the semantic correlations between tests and focal methods based on Pre-trained Code Models (PCMs).TestLinkerfurther establishes mapping rules to accurately link the recommended function name to the concrete production function declaration. Empirical evaluation on a meticulously labeled dataset reveals thatTestLinkersignificantly outperforms traditional static techniques, showing average F1-score improvements ranging from 73.48% to 202.00%. Moreover, compared to state-of-the-art dynamic methods,TestLinker, which only leverages static information, demonstrates comparable or even better performance, with an average F1-score increase of 37.40%.

Coincidental correctness (CC) is a situation during the execution of a test case, the buggy entity is executed, but the program behaves correctly as expected. Many automated fault localization (FL) techniques use runtime information to discover the underlying connection between the executed buggy entity and the failing test result. The existence of CC will weaken such connection, mislead the FL algorithms to build inaccurate models, and consequently, decrease the localization accuracy. To alleviate the adverse effect of CC on FL, CC detection techniques have been proposed to identify the possible CC tests via heuristic or machine learning algorithms. However, their performance on precision is not satisfactory since they overestimate the possible CC tests and are insufficient in learning the deep semantic features. In this work, we propose a novelTriplet network-basedCoincidentalCorrectness detection technique (i.e.,TriCoCo) to overcome the limitations of the prior works.TriCoConarrows the possible CC tests by designing three features to identify genuine passing tests. Instead of using all tests as inputs by existing techniques,TriCoCotakes the identified genuine passing tests and failing ones to train a triplet model that can evaluate their relative distance. Finally,TriCoCoinfers the probability of being a CC test of the test in the rest of the passing tests by using the trained triplet model. We conduct large-scale experiments to evaluateTriCoCobased on the widely-used Defects4J benchmark. The results demonstrate thatTriCoCocan improve not only the precision of CC detection but also the effectiveness of FL techniques,e.g.,the precision ofTriCoCois 80.33$\%$on average, andTriCoCoboosts the efficacy of DStar by 18$\%$–74$\%$in terms of MFR metric when compared to seven state-of-the-art CC detection baselines.

The high quality of input data serves as the foundation for various tasks. Inaccurate data may decrease the effectiveness of elaborate algorithms and significantly impact the output. This also applies to fault localization, as accurate and reliable data is crucial for effective fault localization techniques. Many fault localization techniques analyze the coverage information for detecting bug positions. However, the source coverage data suffers from various problems, such as the imbalanced data and the coincidental correctness. These problems make the source coverage data unreliable for fault localization. To mitigate the potential adverse effect of these unreliable factors, we propose Orlando, a cOveRage-based decoupLing And recoNstructingData apprOach for fault localization. Or-landooptimizes the coverage data by synthesizing passing coverage with less coincidental correctness and failing coverage with more balanced data. The reconstructed data can provide more reliable source data for fault localization. We evaluate Orlando using the widely used Defects4J benchmark and demonstrate its effectiveness in improving two spectrum-based and two deep learning-based methods. Furthermore, Orlando outperforms state-of-the-art data optimization approaches in fault localization.

Mutation testing, a well-suited technology for functional validation, is regrettably poorly studied in hardware. We propose Mantra: the first open-source code-level mutation testing tool based on real hardware bugs. Specifically, Mantra devises time-aware mutation killing mechanism for cost reduction of hardware mutation testing using the parallelism of hardware design code, and then defines and implements 19 hardware mutation operators via large-scale empirical analysis on real bugs. Finally, the evaluation on public datasets from CirFix and OpenCores shows that Mantra achieves promising results with a maximum boost of 83.44%.

Classification tasks are prevalent and play a crucial role in the field of software engineering. However, when two classes exhibit similar features at the class level, the classification model is prone to misclassification, which we refer to as ambiguous classification, and the corresponding classes as ambiguous classes. Ambiguous classification may impact the security and reliability of software engineering classification systems.To correct ambiguous classification, we propose a two-stage framework. Our key insight is to combine two different classification models and utilize their complementary knowledge to maximize the classification ability of the two-stage framework. Specifically, we identify ambiguous classes according to the confusion matrix of the original model. Then, we construct a two-stage model, where the first stage utilizes the original model and the second stage utilizes a different model trained on the same dataset. The second-stage model is responsible for reclassifying the samples that are predicted as ambiguous classes by the first-stage model. We evaluate our method on two software engineering tasks. Experimental results indicate that our method can effectively correct ambiguous classification and achieve a relative improvement of 19.8% in F1-score for ambiguous classes.

A test suite is indispensable for fault localization by providing useful execution information of its test cases for locating suspicious statements of being faulty. There exists a type of test cases known as coincidental correctness (CC) test cases, which executes the faulty statement whereas produces the anticipated output. The existing studies have shown CC test cases harmfully impact fault localization effectiveness. Therefore, it is crucial to detect CC test cases to mitigate the adverse impact of CC test cases on fault localization.To address this issue, we propose ContraCC: a CC test cases detection method using contrastive learning. The insight of ContraCC is that the internal structural information of source test case execution data should be beneficial for CC detection whereas there is a lack of suitable representation methods. Inspired by the insight, ContraCC uses contrastive learning to learn new differentiated representations as test case vectors, which differentiate between similar and dissimilar pairs of test cases by maximizing their similarity within the same class and minimizing it between different classes. Based on the contrastive learning representations (i.e., test case vectors), ContraCC adopts multi-layer perceptron for binary classification to detect CC in downstream tasks. To evaluate the effectiveness of ContraCC, we conduct large-scale experiments on widely-used benchmarks by comparing ContraCC with five state-of-the-art CC test cases detection methods and applying ContraCC for fault localization. The experimental results show that ContraCC outperforms four state-of-the-art methods (e.g., from 10% to 84% improvement in Top-N on the best-performing baseline NeuralCCD) and significantly improves fault localization effectiveness (e.g., 24% improvement on the best-performing baseline Dstar).

Fault localization (FL) analyzes the execution information of a test suite to pinpoint the root cause of a failure. The class imbalance of a test suite, i.e., the imbalanced class proportion between passing test cases (i.e., majority class) and failing ones (i.e., minority class), adversely affects FL effectiveness.To mitigate the effect of class imbalance in FL, we propose CGAN4FL: a data augmentation approach using Context-aware Generative Adversarial Network for Fault Localization. Specifically, CGAN4FL uses program dependencies to construct a failure-inducing context showing how a failure is caused. Then, CGAN4FL leverages a generative adversarial network to analyze the failure-inducing context and synthesize the minority class of test cases (i.e., failing test cases). Finally, CGAN4FL augments the synthesized data into original test cases to acquire a class-balanced dataset for FL. Our experiments show that CGAN4FL significantly improves FL effectiveness, e.g., promoting MLP-FL by 200.00%, 25.49%, and 17.81% under the Top-1, Top-5, and Top-10 respectively.

Unit testing validates the correctness of the unit under test and has become an essential activity in software development process. A unit test consists of a test prefix that drives the unit under test into a particular state, and a test oracle (e.g., assertion), which specifies the behavior in that state. To reduce manual efforts in conducting unit testing, Yu et al. proposed an integrated approach (integration for short), combining information retrieval with a deep learning-based approach, to generate assertions for a unit test. Despite being promising, there is still a knowledge gap as to why or where integration works or does not work. In this paper, we describe an in-depth analysis of the effectiveness of integration. Our analysis shows that: ① The overall performance of integration is mainly due to its success in retrieving assertions. ② integration struggles to understand the semantic differences between the retrieved focal-test (focal-test includes a test prefix and a unit under test) and the input focal-test, resulting in many tokens being incorrectly modified; ③ integration is limited to specific types of edit operations (i.e., replacement) and cannot handle token addition or deletion. To improve the effectiveness of assertion generation, this paper proposes a novel retrieve-and-edit approach named EDITAS. Specifically, Editas first retrieves a similar focal-test from a pre-defined corpus and treats its assertion as a prototype. Then, Editas reuses the information in the prototype and edits the prototype automatically. Editas is more generalizable than integration because it can ❶ comprehensively understand the semantic differences between input and similar focal-tests; ❷ apply appropriate assertion edit patterns with greater flexibility; and ❸ generate more diverse edit actions than just replacement operations. We conduct experiments on two large-scale datasets and the experimental results demonstrate that Editas outperforms the state-of-the-art approaches, with an average improvement of 10.00%-87.48% and 3.30%-42.65% in accuracy and BLEU score, respectively.

Fault localization seeks to locate the suspicious statements possible for causing a program failure. Experimental evidence shows that fault localization effectiveness is affected adversely by the existence of coincidental correctness (CC) test cases, where a CC test case denotes the test case which executes a fault but no failure occurs. Even worse, CC test cases are prevailing in realistic testing and debugging, leading to a severe issue on fault localization effectiveness. Thus, it is indispensable to accurately detect CC test cases and alleviate their harmful effect on fault localization effectiveness.To address this problem, we propose NeuralCCD: a neural coincidental correctness detection approach by integrating multiple features. Specifically, NeuralCCD first leverages suspiciousness score, coverage ratio and similarity to define three CC detection features. Based on these CC detection features and CC labels, NeuralCCD utilizes multi-layer perceptron to learn a different feature-based model for a program, and finally combine the trained models of different programs as an ensemble system to detect CC test cases. To evaluate the effectiveness of NeuralCCD, we conduct large-scale experiments on 247 faulty version of five representative benchmarks and compare NeuralCCD with four state-of-the-art CC detection approaches. The experimental results show that NeuralCCD significantly improves the effectiveness of CC detection, e.g., NeuralCCD yields by at most 109.5%, 93% and 81.3% improvement of Top-1, Top-3 and Top-5 over Tech-I when utilized in Dstar formular.

Abstract Deep‐Learning‐based Fault Localisation (DLFL) leverages deep neural networks to learn the relationship between statement behaviour and program failures, showing promising results. However, since DLFL uses program failures as labels to conduct supervised learning, a labelled dataset is a requisite of applying DLFL. A failure is detected by comparing program output with a test oracle which is the standard answer for the given input. The problem is, test oracles are often difficult, or even impossible to acquire in real life, and that has severely restricted the application of DLFL since we have only unlabelled datasets in most cases. Thus, MetaFL: Metamorphic Fault Localisation Using Weakly Supervised Deep Learning is proposed, to provide a weakly supervised learning solution for DLFL. Instead of using test oracles, MetaFL uses metamorphic relations to prescribe expected behaviour of a program, and defines labels of metamorphic testing groups by verifying integrity in each group of test cases. Hence, a coarse‐grained labelled dataset can be built from the originally unlabelled one, with which DLFL can work now, utilising a weakly supervised learning paradigm. The experiments show that MetaFL yields a performance comparable to plain DLFL under ideal condition (i.e. the labels of datasets are available). MetaFL successfully extends the methodology of DLFL from supervised learning to weakly supervised learning, and a fully labelled dataset is no longer mandatory for applying DLFL.

Automatically transforming developers' natural language descriptions into source code has been a longstanding goal in software engineering research. Two types of approaches have been proposed in the literature to achieve this: code generation, which involves generating a new code snippet, and code search, which involves reusing existing code. However, despite existing efforts, the effectiveness of the state-of-the-art techniques remains limited. To seek for further advancement, our insight is that code generation and code search can help overcome the limitation of each other: the code generator can benefit from feedback on the quality of its generated code, which can be provided by the code searcher, while the code searcher can benefit from the additional training data augmented by the code generator to better understand code semantics. Drawing on this insight, we propose a novel approach that combines code generation and code search techniques using a generative adversarial network (GAN), enabling mutual improvement through the adversarial training. Specifically, we treat code generation and code search as the generator and discriminator in the GAN framework, respectively, and incorporate several customized designs for our tasks. We evaluate our approach in eight different settings, and consistently observe significant performance improvements for both code generation and code search. For instance, when using NatGen, a state-of-the-art code generator, as the generator and GraphCodeBERT, a state-of-the-art code searcher, as the discriminator, we achieve a 32% increase in CodeBLEU score for code generation, and a 12% increase in mean reciprocal rank for code search on a large-scale Python dataset, compared to their original performances.

Many software processes advocate that the test code should co-evolve with the production code. Prior work usually studies such co-evolution based on production-test co-evolution samples mined from software repositories. A production-test co-evolution sample refers to a pair of a test code change and a production code change where the test code change triggers or is triggered by the production code change. The quality of the mined samples is critical to the reliability of research conclusions. Existing studies mined production-test co-evolution samples based on the following assumption: if a test class and its associated production class change together in one commit, or a test class changes immediately after the changes of the associated production class within a short time interval, this change pair should be a production-test co-evolution sample . However, the validity of this assumption has never been investigated. To fill this gap, we present an empirical study, investigating the reasons for test code updates occurring after the associated production code changes, and revealing the pervasive existence of noise in the production-test co-evolution samples identified based on the aforementioned assumption by existing works. We define a taxonomy of such noise, including six categories (i.e., adaptive maintenance, perfective maintenance, corrective maintenance, indirectly related production code update, indirectly related test code update, and other reasons). Guided by the empirical findings, we propose CHOSEN (an identifi C ation met H od O f production-te S t co- E volutio N ) based on a two-stage strategy. CHOSEN takes a test code change and its associated production code change as input, aiming to determine whether the production-test change pair is a production-test co-evolution sample. Such identified samples are the basis of or are useful for various downstream tasks. We conduct a series of experiments to evaluate our method. Results show that (1) CHOSEN achieves an AUC of 0.931 and an F1-score of 0.928, significantly outperforming existing identification methods, and (2) CHOSEN can help researchers and practitioners draw more accurate conclusions on studies related to the co-evolution of production and test code. For the task of Just-In-Time (JIT) obsolete test code detection, which can help detect whether a piece of test code should be updated when developers modify the production code, the test set constructed by CHOSEN can help measure the detection method’s performance more accurately, only leading to 0.76% of average error compared with ground truth. In addition, the dataset constructed by CHOSEN can be used to train a better obsolete test code detection model, of which the average improvements on accuracy, precision, recall, and F1-score are 12.00%, 17.35%, 8.75%, and 13.50% respectively.

Evaluation is the foundation of automated program repair (APR), as it provides empirical evidence on strengths and weaknesses of APR techniques. However, the reliability of such evaluation is often threatened by various introduced biases. Consequently, bias exploration, which uncovers biases in the APR evaluation, has become a pivotal activity and performed since the early years when pioneer APR techniques were proposed. Unfortunately, there is still no methodology to support a systematic comprehension and discovery of evaluation biases in APR, which impedes the mitigation of such biases and threatens the evaluation of APR techniques. In this work, we propose to systematically understand existing evaluation biases by rigorously conducting the first systematic literature review on existing known biases and systematically uncover new biases by building a taxonomy that categorizes evaluation biases. As a result, we identify 17 investigated biases and uncover a new bias in the usage of patch validation strategies. To validate this new bias, we devise and implement an executable framework APRConfig , based on which we evaluate three typical patch validation strategies with four representative heuristic-based and constraint-based APR techniques on three bug datasets. Overall, this article distills 13 findings for bias understanding, discovery, and validation. The systematic exploration we performed and the open source executable framework we proposed in this article provide new insights as well as an infrastructure for future exploration and mitigation of biases in APR evaluation.

Trace data is critical for fault localization (FL) to analyze suspicious statements potentially responsible for a failure. However, existing trace representation meets its bottleneck mainly in two aspects: (1) the trace information of a statement is restricted to a local context (i.e., a test case) without the consideration of a global context (i.e., all test cases of a test suite); (2) it just uses the ‘occurrence’ for representation without strong FL semantics. Thus, we propose UNITE : an infl U ential co N text-Gu I ded T race r E presentation, representing the trace from both global and local contexts with influential semantics for FL. UNITE embodies and implements two key ideas: (1) UNITE leverages the widely used weighting capability from local and global contexts of information retrieval to reflect how important a statement (a word) is to a test case (a document) in all test cases of a test suite (a collection), where a test case (a document) and all test cases of a test suite (a collection) represent local and global contexts respectively; (2) UNITE further elaborates the trace representation from ‘occurrence’ (weak semantics) to ‘influence’ (strong semantics) by combing program dependencies. The large-scale experiments on 12 FL techniques and 20 programs show that UNITE significantly improves FL effectiveness.

For most Open Source Software (OSS) projects, issues and Pull-requests (PR) are the primary means by which stakeholders of a project report and discuss software problems and code changes, and their descriptions are important for people to understand them. To help ensure the informational quality of issue/PR descriptions, GitHub introduced theissue/PR templatefeature, which pre-populates the description for anyone trying to open a new issue/PR. To better understand this feature, we report on a large-scale, mixed-methods empirical study of templates that explores contents, impacts, and perceptions. Our results show that templates typically contain elements to greet contributors, explain project guidelines, and collect relevant information. After template adoption, the monthly volume of incoming issues and PRs decreases, and issues have fewer monthly discussion comments and longer resolution duration. Although both contributors and maintainers positively rated the usefulness of templates from various aspects, they also reported challenges in using templates (e.g., excessive and irrelevant information request) and suggested potential improvements of the template feature (e.g., better user interaction and advanced automation). This work contributes to the informed use and targeted improvement of templates to enhance OSS practitioners’ collaboration and interaction.

Numerous fault localization techniques identify suspicious statements potentially responsible for program failures by discovering the statistical correlation between test results (i.e.,failingorpassing) and the executions of the different statements of a program (i.e.,coveredornot covered). They rarely incorporate a failure context into their suspiciousness evaluation despite the fact that a failure context showing how a failure is produced is useful for analyzing and locating faults. Since a failure context usually contains the transitive relationships among the statements of causing a failure, its relationship complexity becomes one major obstacle for the context incorporation in suspiciousness evaluation of fault localization. To overcome the obstacle, our insight is that leveraging the promising learning ability may be a candidate solution to learn a feasible model for incorporating a failure context into fault localization. Thus, we propose a context-aware neural fault localization approach (CAN). Specifically, CAN represents the failure context by constructing a program dependency graph, which shows how a set of statements interact with each other (i.e., data and control dependencies) to cause a failure. Then, CAN utilizes graph neural networks to analyze and incorporate the context (e.g., the dependencies among the statements) into suspiciousness evaluation. Our empirical results on the 12 large-sized programs show that CAN achieves promising results (e.g., 29.23% faults are ranked within top 5), and it significantly improves the state-of-the-art baselines with a substantial margin.

Verification of hardware design code is crucial for the quality assurance of hardware products. As an indispensable part of verification, localizing faults in the hardware design code is significant for hardware development but is often regarded as a notoriously difficult and time-consuming task. Thus, automated fault localization techniques that could assist manual debugging have attracted much attention in the hardware community. Prior work indicates that existing methods neither fully utilize program dynamic execution information nor lack attention to timing. In this work, we propose Tarsel: a time-aware spectrum-based fault localization approach to help bridge this gap. Tarsel integrates hardware-specific timing information with the program spectrum and captures the changes of executed statements when the state of the hardware program changes to effectively locate faults. The experimental results show that Tarsel successfully locates over half of bugs in the benchmark at Top-3 and about 90% of bugs at Top-5. In addition, Tarsel statistically outperforms the state-of-the-art fault localization approach CirFix under all six typical metrics. In particular, while no bugs are ranked at Top-1 by CirFix, Tarsel successfully locates 11.41% of bugs at Top-1. It brings fresh insights of hardware bug localization to the community.

Data is the fuel to models, and it is still applicable in fault localization (FL). Many existing elaborate FL techniques take the code coverage matrix and failure vector as inputs, expecting the techniques could find the correlation between program entities and failures. However, the input data is high-dimensional and extremely unbalanced since the real-world programs are large in size and the number of failing test cases is much less than that of passing test cases, which are posing severe threats to the effectiveness of FL techniques.

A test suite is indispensable for conducting effective fault localization, and has two classes of tests: passing tests and failing tests. However, in practice, passing tests heavily outnumber failing tests regarding a fault, leading to failing tests being a minority class in contrast to passing tests. Previous work has empirically shown that the lack of failing tests regarding a fault leads to a class-balanced test suite, which tends to hamper fault localization effectiveness.To address this issue, we propose MSGen: a Model-domain Synthesized Failing Test Generation approach. MSGen utilizes the widely used information model of fault localization (i.e., an abstraction of the execution information and test results of a test suite), and uses the minimum variability of the minority feature space to create new synthesized model-domain failing test samples (i.e., synthesized vectors with failing labels defined as the information model) for fault localization. In contrast to traditional test generation directly from the input domain, MSGen seeks to synthesize failing test samples from the model domain. We apply MSGen to 12 state-of-the-art localization approaches and also compare MSGen to 2 representative data optimization approaches. The experimental results show that our synthesized test generation approach significantly improves fault localization effectiveness with up to 51.22%.

Automated fault localization techniques collect runtime information as input data to identify suspicious statement potentially responsible for program failures. To discover the statistical coincidences between test results (i.e., failing or passing) and the executions of the different statements of a program (i.e., executed or not executed), researchers developed a suspiciousness methodology (e.g., spectrum-based formulas and deep neural network models). However, the occurrences of coincidental correctness (CC) which means the faulty statements were executed but the output of the program was right affect the effectiveness of fault localization. Many researchers seek to identify CC tests using cluster analysis. However, the high-dimensional data containing too much noise reduce the effectiveness of cluster analysis.

Smart contracts have been widely and rapidly used to automate financial and business transactions together with blockchains, helping people make agreements while minimizing trusts. With millions of smart contracts deployed on blockchain, various bugs and vulnerabilities in smart contracts have emerged. Following the rapid development of deep learning, many recent studies have used deep learning for vulnerability detection to conduct security checks before deploying smart contracts. These approaches show effective results on detecting whether a smart contract is vulnerable or not whereas their results on locating suspicious statements responsible for the detected vulnerability are still unsatisfactory.

Automated program repair (APR) holds the promise of aiding manual debugging activities. Over a decade of evolution, a broad range of APR techniques have been proposed and evaluated on a set of real-world bug datasets. However, while more and more bugs have been correctly fixed, we observe that the growth of newly fixed bugs by APR techniques has hit a bottleneck in recent years. In this work, we explore the possibility of addressing complicated bugs by proposing TransplantFix, a novel APR technique that leverages graph differencing-based transplantation from the donor method. The key novelty of TransplantFix lies in three aspects: 1) we propose to use a graph-based differencing algorithm to distill semantic fix actions from the donor method; 2) we devise an inheritance-hierarchy-aware code search approach to identify donor methods with similar functionality; 3) we present a namespace transfer approach to effectively adapt donor code.

Code search aims to find code snippets from large-scale code repositories based on the developer's query intent. A significant challenge for code search is the semantic gap between programming language and natural language. Recent works have indicated that deep learning (DL) techniques can perform well by automatically learning the relationships between query and code. Among these DL-based approaches, the state-of-the-art model is TabCS, a two-stage attention-based model for code search. However, TabCS still has two limitations: semantic loss and semantic confusion. TabCS breaks the structural information of code into token-level words of abstract syntax tree (AST), which loses the sequential semantics between words in programming statements, and it uses a co-attention mechanism to build the semantic correlation of code-query after fusing all features, which may confuse the correlations between individual code features and query. In this paper, we propose a code search model named FcarCS (Fine-grained Co-Attentive Representation Learning Model for Semantic Code Search). FcarCS extracts code textual features (i.e., method name, API sequence, and tokens) and structural features that introduce a statement-level code structure. Unlike TabCS, FcarCS splits AST into a series of subtrees corresponding to code statements and treats each subtree as a whole to preserve sequential semantics between words in code statements. FcarCS constructs a new fine-grained co-attention mechanism to learn interdependent representations for each code feature and query, respectively, instead of performing one co-attention process for the fused code features like TabCS. Generally, this mechanism leverages row/column-wise CNN to enable our model to focus on the strongly correlated local information between code feature and Query. We train and evaluate FcarCS on an open Java dataset with 475k and 10k code/query pairs, respectively. Experimental results show that FcarCS achieves an MRR of 0.613, outperforming three state-of-the-art models DeepCS, UNIF, and TabCS, by 117.38%, 16.76%, and 12.68%, respectively. We also performed a user study for each model with 50 real-world queries, and the results show that FcarCS returned code snippets that are more relevant than the baseline models.

Automated fault localization (FL) techniques collect runtime information as input data and then analyze input data to identify the relationship between program statements and failures. They usually take advantages of the statistics of the input data to develop a suspiciousness evaluation methodology (e.g., spectrum-based formulas and deep neural network models) by exploring the underlying correlation rooted in the input data. Thus, the quality of input data is critical for FL. In the actual process of development, developers seek to generate adequate test cases for testing the function or the robustness of a subject program. However, regarding a fault, most test cases are passed test cases and a very few ones are failed test cases since a very small portion of inputs in input domain will lead to a program failure. It means that FL usually faces a problem of imbalanced data, and this problem has been proven to pose an adverse effect on FL effectiveness. To address this problem, we propose BCL-FL: a data augmentation approach based on between-class learning, which produces new synthesized failed test samples by mixing two classes of real test cases (i.e., a passed test case and a failed one) with a random ratio. Specifically, BCL-FL uses the characteristics of real failed test cases to design a data synthesis formula suitable for failed test samples, which can make the synthesized failed test samples closer to real test cases. Since the synthesized data is different from real data, we ingeniously assign a continuous value between 0 and 1 to label the synthesized sample according to the mixing ratio of original labels. We take the synthesized failed test samples and the original test cases as the balanced input data for FL techniques to address the imbalanced data problem. To evaluate the effectiveness of BCL-FL, we conduct large-scale experiments on 287 faulty versions of eight large-sized programs (from ManyBugs and Defects4J) using six state-of-the-art FL approaches. The experimental results show that BCL-FL significantly improves the effectiveness of existing FL techniques, e.g., BCL-FL improves the CNN-FL approach in Top-1, Top-5, and Top-10 by 150%, 136.36%, and 193.1%, respectively.

Fault localization aims at developing an effective methodology identifying suspicious statements potentially responsible for program failures. The spectrum-based fault localization is the widely used methodology by analyzing the statistical coincidences viewed from the spectrum to evaluate the suspiciousness of each statement of being faulty. However, just analyzing statistical coincidences in the coverage information perspective and without combining diverse amount of information may restrict fault localization effectiveness. Thus, this article proposes feature-based fault localization (Feature-FL): A family fault localization methodology of feature-based metrics by combining the feature diversity from the view of program features into suspiciousness evaluation. Specifically,Feature-FLdefines a concept of branching execution probability to abstract program behaviors as the values of features. Then,Feature-FLuses feature selection (i.e., a family of feature-based metrics) to evaluate the relevance of each feature with program failures. Finally,Feature-FLassociates each feature with its corresponding statement, and uses the relevance as the suspiciousness to locate suspicious statements. We present six feature-based metrics forFeature-FL, and conduct an extensive study to evaluate the effectiveness ofFeature-FLand its potential over the state-of-the-art spectrum-based formulas. Our results provide insight into the potential among different feature-based metrics and also showFeature-FLsignificantly outperforms the state-of-the-art spectrum-based formulas, e.g., an averagesavingof at least 30% over spectrum-based formulas in case of real faults.

In Stack Overflow, a question and its answers are defined as a knowledge unit. These knowledge units can be linked together for different purposes, which typically subdivided into four classes: Duplicate, Directly linkable, Indirectly linkable, and Isolated. Developers usually use these linkable knowledge units to search for more targeted information. Prior studies have found that deep learning or SVM technique can effectively predict the class of linkable knowledge units. However, they focus on short-distance semantic relationship but fail to capture global information (semantic relationship between a word and all the words in the same knowledge unit) and ignore joint semantics (semantic relationship between a word with all the words in different knowledge units). To address the issues, we propose a Self-Attention-based contextual semantic aware Linkable Knowledge prediction model (SALKU). SALKU leverages self-attention to pay attention to all the words in a knowledge unit and fully capture the global information needed for each word, then utilizes a variant of self-attention to extract joint semantics between two knowledge units. Experiment results on an existing dataset show that SALKU out-performs the state-of-the-art approaches CNN, Tuning SVM, and Soft-cos SVM in terms of three metrics, respectively. Additionally, SALKU is faster than the three baseline approaches.

Smart contracts with natural economic attributes have been widely and rapidly developed in various fields. However, the bugs and vulnerabilities in smart contracts have brought huge economic losses, which has strengthened people's attention to the security issues of smart contracts. The immutability of smart contracts makes people more willing to conduct security checks before deploying smart contracts. Nonetheless, existing smart contract vulnerability detection techniques are far away from enough: static analysis approaches rely heavily on manually crafted heuristics which is difficult to reuse across different types of vulnerabilities while deep learning based approaches also have unique limitations. In this study, we propose a novel approach, Peculiar, which uses Pre-training technique for detection of smart contract vulnerabilities based on crucial data flow graph. Compared against the traditional data flow graph which is already utilized in existing approach, crucial data flow graph is less complex and does not bring an unnecessarily deep hierarchy, which makes the model easy to focus on the critical features. Moreover, we also involve pre-training technique in our model due to the dramatic improvements it has achieved on a variety of NLP tasks. Our empirical results show that Peculiar can achieve 91.80 % precision and 92.40 % recall in detecting reentrancy vulnerability, one of the most severe and common smart contract vulnerabilities, on 40,932 smart contract files, which is significantly better than the state-of-the-art methods (e.g., Smartcheck achieves 79.37% precision and 70.50% recall). Meanwhile, another experiment shows that Peculiar is more discerning to reentrancy vulnerability than existing approaches. The ablation experiment reveals that both crucial data flow graph and pre-trained model contribute significantly to the performances of Peculiar.

Searching and reusing existing code from a large scale codebase can largely improve developers’ programming efficiency. To support code reuse, early code search models leverage information retrieval (IR) techniques to index a large-scale code corpus and return relevant code according to developers’ search query. However, IR-based models fail to capture the semantics in code and query. To tackle this issue, developers applied deep learning (DL) techniques to code search models. However, these models either are too complex to determine an effective method efficiently or learning for semantic correlation between code and query inadequately.To bridge the semantic gap between code and query effectively and efficiently, we propose a code search model TabCS (Two-stage Attention-Based model for Code Search) in this study. TabCS extracts code and query information from the code textual features (i.e., method name, API sequence, and tokens), the code structural feature (i.e., abstract syntax tree), and the query feature (i.e., tokens). TabCS performs a two-stage attention net-work structure. The first stage leverages attention mechanisms to extract semantics from code and query considering their semantic gap. The second stage leverages a co-attention mechanism to capture their semantic correlation and learn better code/query representation. We evaluate the performance of TabCS on two existing large-scale datasets with 485k and 542k code snippets, respectively. Experimental results show that TabCS achieves an MRR of 0.57 on Hu et al.’s dataset, outperforming three state-of-the-art models CARLCS-CNN, DeepCS, and UNIF by 18%, 70%, 12%, respectively. Meanwhile, TabCS gains an MRR of 0.54 on Husain et al.’s, outperforming CARLCS-CNN, DeepCS, and UNIF by 32%, 76%, 29%, respectively.

Datasets of real-world bugs shipped with human-written patches are intensively used in the evaluation of existing automated program repair (APR) techniques, wherein the human-written patches always serve as the ground truth, for manual or automated assessment approaches, to evaluate the correctness of test-suite adequate patches. An inaccurate human-written patch tangled with other code changes will pose threats to the reliability of the assessment results. Therefore, the construction of such datasets always requires much manual effort on isolating real bug fixes from bug fixing commits. However, the manual work is time-consuming and prone to mistakes, and little has been known on whether the ground truth in such datasets is really accurate.In this paper, we propose DEPTEST, an automated DatasEt Purification technique from the perspective of triggering Tests. Leveraging coverage analysis and delta debugging, DEPTEST can automatically identify and filter out the code changes irrelevant to the bug exposed by triggering tests. To measure the strength of DEPTEST, we run it on the most extensively used dataset (i.e., Defects4J) that claims to already exclude all irrelevant code changes for each bug fix via manual purification. Our experiment indicates that even in a dataset where the bug fix is claimed to be well isolated, 41.01% of human-written patches can be further reduced by 4.3 lines on average, with the largest reduction reaching up to 53 lines. This indicates its great potential in assisting in the construction of datasets of accurate bug fixes. Furthermore, based on the purified patches, we re-dissect Defects4J and systematically revisit the APR of multi-chunk bugs to provide insights for future research targeting such bugs.

Abstract Many fault localization approaches recently utilize deep learning to learn an effective localization model showing a fresh perspective with promising results. However, localization models are generally learned from class imbalance datasets; that is, the number of failing test cases is much fewer than passing test cases. It may be highly susceptible to affect the accuracy of learned localization models. Thus, in this paper, we explore using data resampling to reduce the negative effect of the imbalanced class problem and improve the accuracy of learned models of deep‐learning‐based fault localization. Specifically, for deep‐learning‐based fault localization, its learning feature may require duplicate essential data to enhance the weak but beneficial experience incurred by the class imbalance datasets. We leverage the property of test cases (i.e., passing or failing) to identify failing test cases as the duplicate essential data and propose an iterative oversampling approach to resample failing test cases for producing a class balanced test suite. We apply the test case resampling to representative localization models using deep learning. Our empirical results on eight large‐sized programs with real faults and four large‐sized programs with seeded faults show that the test case resampling significantly improves fault localization effectiveness.

Bug reports are widely used by developers to fix bugs. Due to the lack of experience, reporters may submit numerous invalid bug reports. Manually determining valid bug reports is a laborious task. Automatically identifying valid bug reports can save time and effort for bug analysis. In this paper, we propose a deep learning-based approach to determine and explain valid bug reports using only textual information i.e., summaries and descriptions of bug reports. Convolutional neural network (CNN) is applied to capture their contextual and semantic features. Moreover, by analyzing the spatial structure of CNN, we backtrack the trained CNN model to get phrases that can explain valid bug reports determination. After inspecting the phrases manually, we summarize some valid bug report patterns. We evaluate our approach on five large-scale open-source projects containing a total of 540491 bug reports. On average, across the five projects, our approach achieves 0.85, 0.80, 0.69 and improves the state-of-the-art approach by 8.97%, 9.59%, 9.52% in terms of AUC, F1-score for valid bug reports, and F1-score for invalid bug reports, respectively. From the summarized patterns, we can find that determining valid bug reports is mainly due to three categories of patterns: Attachment, Environment, and Reproduce.

Developers rely on bug reports to fix bugs. The bug reports are usually stored and managed in bug tracking systems. Due to the different expression habits, different reporters may use different expressions to describe the same bug in the bug tracking system. As a result, the bug tracking system often contains many duplicate bug reports. Automatically detecting these duplicate bug reports would save a large amount of effort for bug analysis. Prior studies have found that deep-learning technique is effective for duplicate bug report detection. Inspired by recent Natural Language Processing (NLP) research, in this paper, we propose a duplicate bug report detection approach based on Dual-Channel Convolutional Neural Networks (DC-CNN). We present a novel bug report pair representation, i.e., dual-channel matrix through concatenating two single-channel matrices representing bug reports. Such bug report pairs are fed to a CNN model to capture the correlated semantic relationships between bug reports. Then, our approach uses the association features to classify whether a pair of bug reports are duplicate or not. We evaluate our approach on three large datasets from three open-source projects, including Open Office, Eclipse, Net Beans and a larger combined dataset, and the accuracy of classification reaches 0.9429, 0.9685, 0.9534, 0.9552 respectively. Such performance outperforms the two state-of-the-art approaches which also use deep-learning techniques. The results indicate that our dual-channel matrix representation is effective for duplicate bug report detection.

Searching and reusing existing code from a large-scale codebase, e.g, GitHub, can help developers complete a programming task efficiently. Recently, Gu et al. proposed a deep learning-based model (i.e., DeepCS), which significantly outperformed prior models. The DeepCS embedded codebase and natural language queries into vectors by two LSTM (long and short-term memory) models separately, and returned developers the code with higher similarity to a code search query. However, such embedding method learned two isolated representations for code and query but ignored their internal semantic correlations. As a result, the learned isolated representations of code and query may limit the effectiveness of code search.

Fault localization aims at identifying suspicious statements potentially responsible for failures. The recent rapid progress on deep learning shows the promising potential of many neural network architectures in making sense of data, and more importantly, this potential offers a new prospective probably benefiting fault localization. Thus, this paper proposes CNN-FL: an approach for localizing faults based on convolutional neural networks to explore the promising potential of deep learning in fault localization. Specifically, CNN-FL constructs a convolutional neural network customized for fault localization, and then trains the network with test cases, and finally evaluates the suspiciousness of each statement by testing the trained model using a virtual test set. Our empirical results show that CNN-FL significantly improves fault localization effectiveness.