Runtime Errors Research Articles

The Metrô Rio case study

This paper reports on the Simulink/Stateflow based development of the on-board equipment of the Metrô Rio Automatic Train Protection system. Particular focus is given to the strategies followed to address formal weaknesses and certification issues of the adopted tool-suite. On the development side, constraints on the Simulink/Stateflow semantics have been introduced and design practices have been adopted to gradually achieve a formal model of the system. On the verification side, a two-phase approach based on model-based testing and abstract interpretation has been followed to enforce functional correctness and runtime error freedom. Formal verification has been experimented as a side activity of the project.Quantitative results are presented to assess the overall strategy: the effort required by the design activities is balanced by the effectiveness of the verification tasks enabled by model-based development and automatic code generation.

Static analysis of run-time errors in embedded real-time parallel C programs

Static analysis of run-time errors in embedded real-time parallel C programs

Region-Based RTSJ Memory Management: State of the art

Developing a real-time system in Java requires awareness of memory behaviour in addition to software functional requirements. The Real-Time Specification for Java (RTSJ) introduces a scoped memory model to avoid garbage collection delays in critical real-time applications which need to meet hard real-time constraints. Scoped memory management has certain advantages over garbage collection in terms of predictability. However, developing a real-time application using scoped memory areas (regions) may suffer from both design and runtime errors. Moreover, from a memory footprint perspective, the inability to determine precisely how many scoped memory areas should be used and which objects or threads should be allocated into these scoped memory areas makes using RTSJ problematic for developing real-time systems. In this paper, a survey of the current approaches to improve scoped memory management and new emerging challenges in RTSJ scoped memory management model are presented. Categorizing those problems and challenges provides a picture of the issues researchers have yet to investigate and to support solutions for an optimal scoped memory model. Current approaches and a set of benchmarks used to evaluate current solutions are presented and new research questions in developing real-time Java systems using a scoped memory model are proposed.

Maintainability defects detection and correction: a multi-objective approach

Software defects often lead to bugs, runtime errors and software maintenance difficulties. They should be systematically prevented, found, removed or fixed all along the software lifecycle. However, detecting and fixing these defects is still, to some extent, a difficult, time-consuming and manual process. In this paper, we propose a two-step automated approach to detect and then to correct various types of maintainability defects in source code. Using Genetic Programming, our approach allows automatic generation of rules to detect defects, thus relieving the designer from a fastidious manual rule definition task. Then, we correct the detected defects while minimizing the correction effort. A correction solution is defined as the combination of refactoring operations that should maximize as much as possible the number of corrected defects with minimal code modification effort. We use the Non-dominated Sorting Genetic Algorithm (NSGA-II) to find the best compromise. For six open source projects, we succeeded in detecting the majority of known defects, and the proposed corrections fixed most of them with minimal effort.

A Sound Type System for Typing Runtime Errors

Dynamically typed languages such as Scheme are widely adopted because of their rich expressiveness. However, there is the drawback that dynamic typing cannot detect runtime errors at compile time. In this paper, we propose a type system which enables static detection of runtime errors. The key idea of our approach is to introduce a special type, called the error type, for expressions that cause runtime errors. The proposed type system brings out the benefit of the error type with set-theoretic union, intersection and complement types, recursive types, parametric polymorphism and subtyping. While existing type systems usually ensure that evaluation never causes runtime errors for typed expressions, our system ensures that evaluation always causes runtime errors for expressions typed with the error type. Likewise, our system also ensures that evaluation never causes errors for expressions typed with any type that does not contain the error type. Under the usual definition of subtyping, it is difficult to syntactically prove the soundness of our type system. We redefine subtyping by introducing the notion of intransitive subtyping, and syntactically prove the soundness under the new definition.

Standard Type Soundness for Agents and Artifacts

Formal models, core calculi, and type systems, are important tools for rigorously stating the more subtle details of a language, as well as characterizing and studying its features and the correctness properties of its programs. In this paper we present FAAL (Featherweight Agent and Artifact Language), a formal calculus modelling the agent and artifact program abstractions provided by the simpA agent framework. The formalisation is largely inspired by Featherweight Java. It is based on reduction rules applied in certain evaluation contexts, properly adapted to the concurrency nature of simpA. On top of this calculus we introduce a standard type system and prove its soundness, so as to guarantee that the execution of a well-typed program does not get stuck. Namely, all primitive mechanisms of agents (activity execution), artifacts (eld/property access and step execution), and their interaction (observation and invocation) are guaranteed to be used in a way that is structurally compliant with the corresponding denitions: hence, there will not be run-time errors due to FAAL

Error Rate Estimation for Defective Circuits via Ones Counting

With VLSI circuit feature size scaling down, it is becoming more difficult and expensive to achieve a desired level of yield. Error-tolerance employs defective chips that occasionally produce erroneous yet acceptable results in targeted applications, and has been proposed as one way to increase effective yield. These chips are characterized by criteria set by specific applications. Error rate, an upper-bound on how frequent errors occur at an output, is one such criterion. In this article we focus on the following problem: given a combinational logic circuit that is defective, and hence occasionally produces an erroneous output, how can we determine the error rate of each output line by using ones counting? The results of this work can also be used for runtime error estimation in aging systems and in environments where soft-errors are produced.

Safe Iterator Framework for the C++ Standard Template Library

The C++ Standard Template Library is the flagship example for libraries based on the generic programming paradigm. The usage of this library is intended to minimize classical C/C++ errors, but does not warrant bug-free programs. Furthermore, many new kinds of errors may arise from the inaccurate use of the generic programming paradigm, like dereferencing invalid iterators or misunderstanding remove-like algorithms. In this paper we present some typical scenarios that may cause undefined or weird behaviour. We present approaches that can be used for developing different safe iterators to avoid run-time errors. Some of these iterators are able to manipulate the container directly, hence they cannot result in undefined behaviour when an algorithm needs to add elements to the container or delete elements from the container. Our iterators are able to indicate if they are invalid. Algorithms’ preconditions are evaluated with our iterators.

Safe locking for multi-threaded Java with exceptions

There are many mechanisms for concurrency control in high-level programming languages. In Java, the original mechanism for concurrency control, based on synchronized blocks, is lexically scoped. For more flexible control, Java 5 introduced non-lexical lock primitives on re-entrant locks.These operators may lead to run-time errors and unwanted behavior; e.g., taking a lock without releasing it, which could lead to a deadlock, or trying to release a lock without owning it. This paper develops a static type and effect system to prevent the mentioned lock errors for a formal, object-oriented calculus which supports non-lexical lock handling and exceptions.Based on an operational semantics, we prove soundness of the effect type analysis. Challenges in the design of the effect type system are dynamic creation of threads, objects, and especially of locks, aliasing of lock references, passing of lock references between threads, and reentrant locks as found in Java. Furthermore, the exception handling mechanism complicates the control-flow and thus the analysis.

Formal Verification of Numerical Programs: From C Annotated Programs to Mechanical Proofs

Numerical programs may require a high level of guarantee. This can be achieved by applying formal methods, such as machine-checked proofs. But these tools handle mathematical theorems while we are interested in C code, in which numerical computations are performed using floating-point arithmetic, whereas proof tools typically handle exact real arithmetic. To achieve this high level of confidence on C programs, we use a chain of tools: Frama-C, its Jessie plugin, Why and provers among Coq, Gappa, Alt-Ergo, CVC3 and Z3. This approach requires the C program to be annotated: each function must be precisely specified, and we prove the correctness of the program by proving both that it meets its specifications and that no runtime error may occur. The purpose of this paper is to illustrate, on various examples, the features of this approach.

Rigorous software development: an introduction to program verification

The use of mathematical methods in the development of software is essential when reliable systems are sought; in particular they are now strongly recommended by the official norms adopted in the production of critical software. Program Verification is the area of computer science that studies mathematical methods for checking that a program conforms to its specification. This text is a self-contained introduction to program verification using logic-based methods, presented in the broader context of formal methods for software engineering.The idea of specifying the behaviour of individual software components by attaching contracts to them is now a widely followed approach in program development, which has given rise notably to the development of a number of behavioural interface specification languages and program verification tools. A foundation for the static verification of programs based on contract-annotated routines is laid out in the book. These can be independently verified, which provides a modular approach to the verification of software.The text assumes only basic knowledge of standard mathematical concepts that should be familiar to any computer science student. It includes a self-contained introduction to propositional logic and first-order reasoning with theories, followed by a study of program verification that combines theoretical and practical aspects - from a program logic (a variant of Hoare logic for programs containing user-provided annotations) to the use of a realistic tool for the verification of C programs (annotated using the ACSL specification language), through the generation of verification conditions and the static verification of runtime errors.

Gem #68

In this Gem and the next one, we present a simple walk-through of SPARK's capabilities and its integration with GPS. In this first Gem, we show how to set up a SPARK project and prove that your SPARK programs are free from uninitialized variable accesses and that they execute without run-time errors.

Gem #69

In this Gem and the previous one, we give you a simple walkthrough of SPARK's capabilities and its integration with GPS. In the previous Gem, we showed how to set up a SPARK project and prove that your SPARK programs are free from uninitialized variable accesses and that they execute without run-time errors. In this Gem, we show how to prove that your SPARK programs respect given contracts.

A qualitative human-centric evaluation of flexibility in middleware implementations

Today middleware is much more powerful, more reliable and faster than it used to be. Nevertheless, for the application developer, the complexity of using middleware platforms has increased accordingly. The volume and variety of application contexts that current middleware technologies have to support require that developers be able to anticipate the widest possible range of execution environments, desired and undesired effects of different programming strategies, handling procedures for runtime errors, and so on. This paper shows how a generic framework designed to evaluate the usability of notations (the Cognitive Dimensions of Notations Framework, or CDN) has been instantiated and used to analyze the cognitive challenges involved in adapting middleware platforms. This human-centric perspective allowed us to achieve novel results compared to existing middleware evaluation research, typically centered around system performance metrics. The focus of our study is on the process of adapting middleware implementations, rather than in the end product of this activity. Our main contributions are twofold. First, we describe a qualitative CDN-based method to analyze the cognitive effort made by programmers while adapting middleware implementations. And second, we show how two platforms designed for flexibility have been compared, suggesting that certain programming language design features might be particularly helpful for developers.

The Pain of Implementing LINQ Providers

I remember sitting on the edge of my seat watching the 2005 PDC (Professional Developers Conference) videos that first showed LINQ (Language Integrated Query). I wanted LINQ: it offered just about everything that I could hope for to make working with data easy. The impetus for building queries into the language is quite simple; it is something that is used all the time; and the promise of a unified querying model is good enough, even before you add all the language goodies that were dropped on us. Being able to write in C# and have the database magically understand what I am doing? Awesome! Getting compilation errors from Visual Studio, rather than runtime errors at testing (or worse, production)? Wonderful! Getting rid of most SQL injection issues? Amazing!

Dependence-based multi-level tracing and replay for wireless sensor networks debugging

Due to resource constraints and unreliable communication, wireless sensor network (WSN) programming and debugging remain to be a challenging task. Runtime errors must be constantly monitored, often by checking for violations of certain invariants. Once an error is detected, diagnosis must be performed to identify the origin of the error. Deterministic replay is an error diagnosis method which has long been proposed for distributed systems. However, one of the significant hurdles for applying deterministic replay on WSN is posed by the small program memory on typical sensor nodes. This paper proposes a dependence-based multi-level method for memory-efficient tracing and replay. In the interest of portability across different hardware platforms, the method is implemented as a source-level tracing and replaying tool. To further reduce the code size after tracing instrumentation, a cost model is used for making the decision on which functions to in-line. A prototype for the tool targets C programs is developed on top of the Open64 compiler and is tested using several TinyOS applications running on TelosB motes. Preliminary experimental results show that the test programs, which do not fit the program memory after straightforward instrumentation, can be successfully accommodated in memory using the new method such that the injected errors can be found.

Reconstruction of Type Information from Java Bytecode for Component Compatibility

The Java type system is strictly checked by both the compiler and the runtime bytecode interpreter of the JVM. These mechanisms together guarantee appropriate usage of class instances. Using modern component systems can however circumvent these static checks, because incompatible versions of classes can be bound together during component installation or update. Such problematic bindings result in ClassCastException or NoSuchMethodException runtime errors. In this paper we describe a representation of Java language types suitable for checking component compatibility. The presented approach applies various bytecode handling techniques to reconstruct a representation of the Java types contained in a component implementation, using different sources of class data. The representation is then used during build- and run-time type system verifications with the aim to prevent these kinds of errors. We have successfully applied this approach to prevent OSGi component incompatibilities.

Static analysis by abstract interpretation of embedded critical software

Formal methods are increasingly used to help ensuring the correctness of complex, critical embedded software systems. We show how sound semantic static analyses based on Abstract Interpretation may be used to check properties at various levels of a software design: from high level models to low level binary code. After a short introduction to the Abstract Interpretation theory, we present a few current applications: checking for run-time errors at the C level, translation validation from C to assembly, and analyzing SAO models of communicating synchronous systems with imperfect clocks. We conclude by briey proposing some requirements to apply Abstract Interpretation to modeling languages such as UML.

Reliability-Driven ECC Allocation for Multiple Bit Error Resilience in Processor Cache

With increasing parameter variations in nanometer technologies, on-chip cache in processor is becoming highly vulnerable to runtime failures induced by “soft error,” voltage, or thermal noise and aging effects. Nondeterministic and unreliable memory operation due to these runtime failures can be addressed by: 1) designing the memory for worst-case scenarios and/or 2) runtime error detection and correction. Worst-case guard-banding can lead to overly pessimistic results for cell footprint and power. On the other hand, conventional error correcting code (ECC) used in processor cache has very limited correction capability, making it insufficient to protect memory in scaled technologies (sub-45 nm), which are vulnerable to multiple-bit failures in a word (64-bit). The requirement to tolerate multibit failures is accentuated with supply voltage scaling for low-power operation. We note that due to inter and intra-die parameter variations, different memory blocks move to different reliability corners. A uniform ECC protection for all memory blocks fails to account for the distribution of vulnerability across memory blocks. On the other hand, it can lead to overly pessimistic results if the worst-case vulnerability of a memory block is accounted for during ECC allocation. In this paper, we propose a reliability-driven ECC allocation scheme that matches the relative vulnerability of a memory block (determined using postfabrication characterization) with appropriate ECC protection. We achieve postfabrication variable ECC allocation by storing the check bits in the “ways” of an associative cache. We use shortened Bose-Chaudhuri-Hocquenghem (BCH) cyclic code with zero padding, which provides high random error correction capability with modest amount of check bits. Moreover, we propose efficient circuit/architecture-level optimizations of the ECC encoding/decoding logic to minimize the impact on area, performance, and energy. Simulation results for SPEC2000 benchmarks show that such a variable ECC scheme tolerates high failure rates with negligible performance (four percent) and area (0.2 percent) penalty.

웹기반 프로그래밍 언어 강의 지원 시스템의 설계 및 구현

In this paper, we propose a web-based programming class support system to help a lecturer to teach a programming language to students effectively. The proposed system is composed of a error analysis step and a verification step. The error analysis step checks whether there are compile time errors or run time errors in each student`s submitted program. Given some errors, the system provides helpful feedback for the student to fix the errors. On the contrary, the system provides quick feedback after checking the source code style, comments, and plagiarism in the submitted program. As soon as the student submits the program, the student can see the check results. According to the result of utilizing the proposed system in a C programming language class, students tend to submit program assignments actively.