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Finding Compiler Bugs via Live Code Mutation

acm sigplan NOTICES 2016年第10期51卷 849-863页

作者： Sun, Chengnian Vu Le Su, Zhendong Univ Calif Davis Dept Comp Sci Davis CA 95616 USA

Validating optimizing compilers is challenging because it is hard to generate valid test programs (i.e., those that do not expose any undefined behavior). Equivalence Modulo Inputs (EMI) is an effective, promising methodology to tackle this problem. Given a test program with some inputs, EMI mutates the program to derive variants that are semantically equivalent w.r.t. these inputs. The state-of-the-art instantiations of EMI are Orion and Athena, both of which rely on deleting code from or inserting code into code regions that are not executed under the inputs. Although both have demonstrated their ability in finding many bugs in GCC and LLVM, they are still limited due to their mutation strategies that operate only on dead code regions. This paper presents a novel EMI technique that allows mutation in the entire program (i.e., both live and dead regions). By removing the restriction of mutating only the dead regions, our technique significantly increases the EMI variant space. It also helps to more thoroughly stress test compilers as compilers must optimize mutated live code, whereas mutated dead code might be eliminated. Finally, our technique also makes compiler bugs more noticeable as miscompilations on mutated dead code may not be observable. We have realized the proposed technique in Hermes. The evaluation demonstrates Hermes's effectiveness. In 13 months, Hermes found 168 confirmed, valid bugs in GCC and LLVM, of which 132 have already been fixed.

关键词： Compiler testing miscompilation equivalent program variants automated testing Algorithms languages Reliability Verification

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Checks and Balances Constraint Solving without Surprises in object-Constraint programming languages 2015

Checks and Balances Constraint Solving without Surprises in ...

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acm sigplan international conference on object-oriented programming, systems, languages, and Applications (OOPSLA)

作者： Felgentreff, Tim Millstein, Todd Borning, Alan Hirschfeld, Robert Viewpoints Res Inst CDG SAP Labs Potsdam Germany Hasso Plattner Inst Potsdam Germany Univ Calif Los Angeles Los Angeles CA USA Univ Washington Seattle WA 98195 USA

ISBN: (纸本)9781450336895

object-constraint programming systems integrate declarative constraint solving with imperative, object-oriented languages, seamlessly providing the power of both paradigms. However, experience with object-constraint systems has shown that giving too much power to the constraint solver opens up the potential for solutions that are surprising and unintended as well as for complex interactions between constraints and imperative code. On the other hand, systems that overly limit the power of the solver, for example by disallowing constraints involving mutable objects, object identity, or polymorphic message sends, run the risk of excluding the core object-oriented features of the language from the constraint part, and consequently not being able to express declaratively a large set of interesting problem solutions. In this paper we present design principles that tame the power of the constraint solver in object-constraint languages to avoid difficult corner cases and surprising solutions while retaining the key features of the approach, including constraints over mutable objects, constraints involving object identity, and constraints on the results of message sends. We present our solution concretely in the context of the Babelsberg object-constraint language framework, providing both an informal description of the resulting language and a formal semantics for a core subset of it. We validate the utility of this semantics with an executable version that allows us to run test programs and to verify that they provide the same results as existing implementations of Babelsberg in JavaScript, Ruby, and Smalltalk.

关键词： Constraints object-Constraint programming Constraint Imperative programming Executable Semantics Test Suites

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Hybrid STM/HTM for Nested Transactions on OpenJDK

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acm sigplan NOTICES 2016年第10期51卷 660-676页

作者： Chapman, Keith Hosking, Antony L. Moss, J. Eliot B. Purdue Univ W Lafayette IN 47907 USA Australian Natl Univ Data61 Canberra ACT Australia Univ Massachusetts Amherst MA USA

Transactional memory (TM) has long been advocated as a promising pathway to more automated concurrency control for scaling concurrent programs running on parallel hardware. Software TM (STM) has the benefit of being able to run general transactional programs, but at the significant cost of overheads imposed to log memory accesses, mediate access conflicts, and maintain other transaction metadata. Recently, hardware manufacturers have begun to offer commodity hardware TM (HTM) support in their processors wherein the transaction metadata is maintained "for free" in hardware. However, HTM approaches are only best-effort: they cannot successfully run all transactional programs, whether because of hardware capacity issues (causing large transactions to fail), or compatibility restrictions on the processor instructions permitted within hardware transactions (causing transactions that execute those instructions to fail). In such cases, programs must include failure-handling code to attempt the computation by some other software means, since retrying the transaction would be futile. Thus, a canonical use of HTM is lock elision: replacing lock regions with transactions, retrying some number of times in the case of conflicts, but falling back to locking when HTM fails for other reasons. Here, we describe how software and hardware schemes can combine seamlessly into a hybrid system in support of transactional programs, allowing use of low-cost HTM when it works, but reverting to STM when it doesn't. We describe heuristics used to make this choice dynamically and automatically, but allowing the transition back to HTM opportunistically. Our implementation is for an extension of Java having syntax for both open and closed nested transactions, and boosting, running on the OpenJDK, with dynamic injection of STM mechanisms (into code variants used under STM) and HTM instructions (into code variants used under HTM). Both schemes are compatible to allow different threads to run concur

关键词： transactional memory nested transactions hardware transactional memory software transactional memory Java Design Experimentation languages Measurement Performance

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Accurate Profiling in the Presence of Dynamic Compilation 2015

Accurate Profiling in the Presence of Dynamic Compilation

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acm sigplan international conference on object-oriented programming, systems, languages, and Applications (OOPSLA)

作者： Zheng, Yudi Bulej, Lubomir Binder, Walter USI Fac Informat Lugano Switzerland Charles Univ Prague Fac Math & Phys CR-11636 Prague 1 Czech Republic

ISBN: (纸本)9781450336895

Many profilers based on bytecode instrumentation yield wrong results in the presence of an optimizing dynamic compiler, either due to not being aware of optimizations such as stack allocation and method inlining, or due to the inserted code disrupting such optimizations. To avoid such perturbations, we present a novel technique to make any profiler implemented at the bytecode level aware of optimizations performed by the dynamic compiler. We implement our approach in a state-of-the-art Java virtual machine and demonstrate its significance with concrete profilers. We quantify the impact of escape analysis on allocation profiling, object lifetime analysis, and the impact of method inlining on callsite profiling. We illustrate how our approach enables new kinds of profilers, such as a profiler for non-inlined callsites, and a testing framework for locating performance bugs in dynamic compiler implementations.

关键词： Algorithms languages Measurement Performance Dynamic compilers profiling bytecode instrumentation

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How Scale Affects Structure in Java Programs 2015

How Scale Affects Structure in Java Programs

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acm sigplan international conference on object-oriented programming, systems, languages, and Applications (OOPSLA)

作者： Lopes, Cristina V. Ossher, Joel Univ Calif Irvine Bren Sch Informat & Comp Sci Irvine CA 92697 USA

ISBN: (纸本)9781450336895

Many internal software metrics and external quality attributes of Java programs correlate strongly with program size. This knowledge has been used pervasively in quantitative studies of software through practices such as normalization on size metrics. This paper reports size-related super- and sublinear effects that have not been known before. Findings obtained on a very large collection of Java programs - 30,911 projects hosted at Google Code as of Summer 2011 - unveils how certain characteristics of programs vary disproportionately with program size, sometimes even non-monotonically. Many of the specific parameters of nonlinear relations are reported. This result gives further in-sights for the differences of "programming in the small" vs. "programming in the large." The reported findings carry important consequences for OO software metrics, and software research in general: metrics that have been known to correlate with size can now be properly normalized so that all the information that is left in them is size-independent.

关键词： object oriented Programs Metrics Linear Regression Models

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Towards transitory encapsulation

Towards transitory encapsulation

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acm sigplan international conference on systems, programming, languages and Applications: Software for Humanity, SPLASH 2015

作者： Fleissner, Sebastian Research School of Computer Science Australian National University Australia

ISBN: (纸本)9781450337229

Encapsulation and information hiding are essential and fundamental to object-oriented and aspect-oriented programming languages. These principles ensure that one part of a program does not depend on assumptions on the internal structure and logic of other parts of the program. While this assumption allows for clearly defined modules, interfaces and interaction protocols when software is initially developed, it is possible that rigid encapsulation causes problems, such as brittleness, as software changes and evolves over time. We suggest that, just as the strength of type systems have relaxed over time, perhaps structural boundaries could, too be relaxed. Perhaps there could be a new kind of flexible encapsulation: one that allows non-permanent and flexible boundaries between program parts.

关键词： Aspect oriented programming

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GTInspector: A moldable domain-aware object inspector

GTInspector: A moldable domain-aware object inspector

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acm sigplan international conference on systems, programming, languages and Applications: Software for Humanity, SPLASH 2015

作者： Chiş, Andrei Nierstrasz, Oscar Syrel, Aliaksei Gîrba, Tudor Software Composition Group University of Bern Switzerland

ISBN: (纸本)9781450337229

Understanding the run-time behaviour of object-oriented applications entails the comprehension of run-time objects. Traditional object inspectors favor generic views that focus on the low-level details of the state of single objects. While universally applicable, this generic approach does not take into account the varying needs of developers that could benefit from tailored views and exploration possibilities. GTIn-spector is a novel moldable object inspector that provides different high-level ways to visualize and explore objects, adapted to both the object and the current developer need. More information about the GTInspector can be found at: ***/research/moldableinspector.

关键词： object oriented programming

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Approximate Computation with Outlier Detection in Topaz 2015

Approximate Computation with Outlier Detection in Topaz

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acm sigplan international conference on object-oriented programming, systems, languages, and Applications (OOPSLA)

作者： Achour, Sara Rinard, Martin C. MIT CSAIL Cambridge MA 02139 USA

ISBN: (纸本)9781450336895

We present Topaz, a new task-based language for computations that execute on approximate computing platforms that may occasionally produce arbitrarily inaccurate results. Topaz maps tasks onto the approximate hardware and integrates the generated results into the main computation. To prevent unacceptably inaccurate task results from corrupting the main computation, Topaz deploys a novel outlier detection mechanism that recognizes and precisely reexecutes outlier tasks. Outlier detection enables Topaz to work effectively with approximate hardware platforms that have complex fault characteristics, including platforms with bit pattern dependent faults (in which the presence of faults may depend on values stored in adjacent memory cells). Our experimental results show that, for our set of benchmark applications, outlier detection enables Topaz to deliver acceptably accurate results (less than 1% error) on our target approximate hardware platforms. Depending on the application and the hardware platform, the overall energy savings range from 5 to 13 percent. Without outlier detection, only one of the applications produces acceptably accurate results.

关键词： languages Reliability Performance Approximate Computing Control systems Dynamic systems

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Scrap Your Boilerplate with object Algebras 2015

Scrap Your Boilerplate with Object Algebras

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acm sigplan international conference on object-oriented programming, systems, languages, and Applications (OOPSLA)

作者： Zhang, Haoyuan Chu, Zewei Oliveira, Bruno C. D. S. van der Storm, Tijs Univ Hong Kong Hong Kong Hong Kong Peoples R China CWI Amsterdam Netherlands

ISBN: (纸本)9781450336895

Traversing complex Abstract Syntax Trees (ASTs) typically requires large amounts of tedious boilerplate code. For many operations most of the code simply walks the structure, and only a small portion of the code implements the functionality that motivated the traversal in the first place. This paper presents a type-safe Java framework called Shy that removes much of this boilerplate code. In Shy object Algebras are used to describe complex and extensible AST structures. Using Java annotations Shy generates generic boilerplate code for various types of traversals. For a concrete traversal, users of Shy can then inherit from the generated code and override only the interesting cases. Consequently, the amount of code that users need to write is significantly smaller. Moreover, traversals using the Shy framework are also much more structure shy, becoming more adaptive to future changes or extensions to the AST structure. To prove the effectiveness of the approach, we applied Shy in the implementation of a domain-specific questionnaire language. Our results show that for a large number of traversals there was a significant reduction in the amount of user-defined code.

关键词： languages object algebras boilerplate code Java adaptive object-oriented programming

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Synthesizing Java Expressions from Free-Form Queries 2015

Synthesizing Java Expressions from Free-Form Queries

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acm sigplan international conference on object-oriented programming, systems, languages, and Applications (OOPSLA)

作者： Gvero, Tihomir Kuncak, Viktor Ecole Polytech Fed Lausanne CH-1015 Lausanne Switzerland

ISBN: (纸本)9781450336895

We present a new code assistance tool for integrated development environments. Our system accepts as input free-form queries containing a mixture of English and Java, and produces Java code expressions that take the query into account and respect syntax, types, and scoping rules of Java, as well as statistical usage patterns. In contrast to solutions based on code search, the results returned by our tool need not directly correspond to any previously seen code fragment. As part of our system we have constructed a probabilistic context free grammar for Java constructs and library invocations, as well as an algorithm that uses a customized natural language processing tool chain to extract information from free-form text queries. We present the results on a number of examples showing that our technique (1) often produces the expected code fragments, (2) tolerates much of the flexibility of natural language, and (3) can repair incorrect Java expressions that use, for example, the wrong syntax or missing arguments.

关键词： Algorithms languages Theory Program Synthesis Natural Language Processing Autocompletion Program Repair

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