Soundly Handling Static Fields: Issues, Semantics and Analysis

Although in most cases class initialization works as expected, some static fields may be read before being initialized, despite being initialized in their corresponding class initializer. We propose an analysis which compute, for each program point, the set of static fields that must have been initialized and discuss its soundness. We show that such an analysis can be directly applied to identify the static fields that may be read before being initialized and to improve the precision while preserving the soundness of a null-pointer analysis.Comment: Proceedings of the Fourth Workshop on Bytecode Semantics, Verification, Analysis and Transformation (BYTECODE 2009

A comparison of eager and lazy class initialization in Java

We prove that under some natural condition eager class initialization of a Java program P, as proposed in Kozen and Stillerman (2002), does not depend on the choice of a topological sort of the graph of class initialization dependencies of P. We also identify further natural conditions under which the eager and lazy class initializations of P assign the same initial values to the static fields of P. The latter result partially solves a problem raised in Kozen and Stillerman (2002)

Low‐latency Java communication devices on RDMA‐enabled networks

This is the peer reviewed version of the following article: Expósito, R. R., Taboada, G. L., Ramos, S., Touriño, J., & Doallo, R. (2015). Low‐latency Java communication devices on RDMA‐enabled networks. Concurrency and Computation: Practice and Experience, 27(17), 4852-4879., which has been published in final form at https://doi.org/10.1002/cpe.3473. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Use of Self-Archived Versions.[Abstract] Providing high‐performance inter‐node communication is a key capability for running high performance computing applications efficiently on parallel architectures. In fact, current systems deployments are aggregating a significant number of cores interconnected via advanced networking hardware with Remote Direct Memory Access (RDMA) mechanisms, that enable zero‐copy and kernel‐bypass features. The use of Java for parallel programming is becoming more promising thanks to some useful characteristics of this language, particularly its built‐in multithreading support, portability, easy‐to‐learn properties, and high productivity, along with the continuous increase in the performance of the Java virtual machine. However, current parallel Java applications generally suffer from inefficient communication middleware, mainly based on protocols with high communication overhead that do not take full advantage of RDMA‐enabled networks. This paper presents efficient low‐level Java communication devices that overcome these constraints by fully exploiting the underlying RDMA hardware, providing low‐latency and high‐bandwidth communications for parallel Java applications. The performance evaluation conducted on representative RDMA networks and parallel systems has shown significant point‐to‐point performance increases compared with previous Java communication middleware, allowing to obtain up to 40% improvement in application‐level performance on 4096 cores of a Cray XE6 supercomputer.Ministerio de Economía y Competitividad; TIN2013-42148-PXunta de Galicia; GRC2013/055Ministerio de Educación y Ciencia; AP2010-434

What the Smell? An Empirical Investigation on the Distribution and Severity of Test Smells in Open Source Android Applications

The widespread adoption of mobile devices, coupled with the ease of developing mobile-based applications (apps) has created a lucrative and competitive environment for app developers. Solely focusing on app functionality and time-to-market is not enough for developers to ensure the success of their app. Quality attributes exhibited by the app must also be a key focus point; not just at the onset of app development, but throughout its lifetime. The impact analysis of bad programming practices, or code smells, in production code has been the focus of numerous studies in software maintenance. Similar to production code, unit tests are also susceptible to bad programming practices which can have a negative impact not only on the quality of the software system but also on maintenance activities. With the present corpus of studies on test smells primarily on traditional applications, there is a need to fill the void in understanding the deviation of testing guidelines in the mobile environment. Furthermore, there is a need to understand the degree to which test smells are prevalent in mobile apps and the impact of such smells on app maintenance. Hence, the purpose of this research is to: (1) extend the existing set of bad test-code practices by introducing new test smells, (2) provide the software engineering community with an open-source test smell detection tool, and (3) perform a large-scale empirical study on test smell occurrence, distribution, and impact on the maintenance of open-source Android apps. Through multiple experiments, our findings indicate that most Android apps lack an automated verification of their testing mechanisms. As for the apps with existing test suites, they exhibit test smells early on in their lifetime with varying degrees of co-occurrences with different smell types. Our exploration of the relationship between test smells and technical debt proves that test smells are a strong measurement of technical debt. Furthermore, we observed positive correlations between specific smell types and highly changed/buggy test files. Hence, this research demonstrates that test smells can be used as indicators for necessary preventive software maintenance for test suites

On the Distribution of Test Smells in Open Source Android Applications: An Exploratory Study

The impact of bad programming practices, such as code smells, in production code has been the focus of numerous studies in software engineering. Like production code, unit tests are also affected by bad programming practices which can have a negative impact on the quality and maintenance of a software system. While several studies addressed code and test smells in desktop applications, there is little knowledge of test smells in the context of mobile applications. In this study, we extend the existing catalog of test smells by identifying and defining new smells and survey over 40 developers who confirm that our proposed smells are bad programming practices in test suites. Additionally, we perform an empirical study on the occurrences and distribution of the proposed smells on 656 open-source Android apps. Our findings show a widespread occurrence of test smells in apps. We also show that apps tend to exhibit test smells early in their lifetime with different degrees of co-occurrences on different smell types. This empirical study demonstrates that test smells can be used as an indicator for necessary preventive software maintenance for test suites

A Survey of Symbolic Execution Techniques

Many security and software testing applications require checking whether certain properties of a program hold for any possible usage scenario. For instance, a tool for identifying software vulnerabilities may need to rule out the existence of any backdoor to bypass a program's authentication. One approach would be to test the program using different, possibly random inputs. As the backdoor may only be hit for very specific program workloads, automated exploration of the space of possible inputs is of the essence. Symbolic execution provides an elegant solution to the problem, by systematically exploring many possible execution paths at the same time without necessarily requiring concrete inputs. Rather than taking on fully specified input values, the technique abstractly represents them as symbols, resorting to constraint solvers to construct actual instances that would cause property violations. Symbolic execution has been incubated in dozens of tools developed over the last four decades, leading to major practical breakthroughs in a number of prominent software reliability applications. The goal of this survey is to provide an overview of the main ideas, challenges, and solutions developed in the area, distilling them for a broad audience. The present survey has been accepted for publication at ACM Computing Surveys. If you are considering citing this survey, we would appreciate if you could use the following BibTeX entry: http://goo.gl/Hf5FvcComment: This is the authors pre-print copy. If you are considering citing this survey, we would appreciate if you could use the following BibTeX entry: http://goo.gl/Hf5Fv

Dynamic Test Generation with Static Fields and Initializers

Abstract. Static state is common in object-oriented programs. How-ever, automatic test case generators do not take into account the po-tential interference of static state with a unit under test and may, thus, miss subtle errors. In particular, existing test case generators do not treat static fields as input to the unit under test and do not control the execu-tion of static initializers. We address these issues by presenting a novel technique in automatic test case generation based on static analysis and dynamic symbolic execution. We have applied this technique on a suite of open-source applications and found errors that go undetected by ex-isting test case generators. Our experiments show that this problem is relevant in real code, indicate which kinds of errors existing techniques miss, and demonstrate the effectiveness of our technique.