2672107
Improving the Decompilation of Java Bytecode to Prolog by Partial Evaluation
The interpretative approach to compilation allows compiling programs by partially evaluating an interpreter w.r.t. a source program. This approach, though very attractive in principle, has not been widely applied in practice mainly because of the difficulty in finding a partial evaluation strategy which always obtain ''quality'' compiled programs. In spite of this, in recent work we have performed a proof of concept of that, at least for some examples, this approach can be applied to decompile Java bytecode into Prolog. This allows applying existing advanced tools for analysis of logic programs in order to verify Java bytecode. However, successful partial evaluation of an interpreter for (a realistic subset of) Java bytecode is a rather challenging problem. The aim of this work is to improve the performance of the decompilation process above in two respects. First, we would like to obtain quality decompiled programs, i.e., simple and small. We refer to this as the effectiveness of the decompilation. Second, we would like the decompilation process to be as efficient as possible, both in terms of time and memory usage, in order to scale up in practice. We refer to this as the efficiency of the decompilation. With this aim, we propose several techniques for improving the partial evaluation strategy. We argue that our experimental results show that we are able to improve significantly the efficiency and effectiveness of the decompilation process.
1843951
Cost Analysis of Java Bytecode
Cost analysis of Java bytecode is complicated by its unstructured control flow, the use of an operand stack and its object-oriented programming features (like dynamic dispatching). This paper addresses these problems and develops a generic framework for the automatic cost analysis of sequential Java bytecode. Our method generates cost relations which define at compile-time the cost of programs as a function of their input data size. To the best of our knowledge, this is the first approach to the automatic cost analysis of Java bytecode.
16564830
A Flexible, (C)LP-Based Approach to the Analysis of Object-Oriented Programs
Static analyses of object-oriented programs usually rely on intermediate representations that respect the original semantics while having a more uniform and basic syntax. Most of the work involving object-oriented languages and abstract interpretation usually omits the description of that language or just refers to the Control Flow Graph (CFG) it represents. However, this lack of formalization on one hand results in an absence of assurances regarding the correctness of the transformation and on the other it typically strongly couples the analysis to the source language. In this work we present a framework for analysis of object-oriented languages in which in a first phase we transform the input program into a representation based on Horn clauses. This facilitates on one hand proving the correctness of the transformation attending to a simple condition and on the other allows applying existing analyzers for (constraint) logic programming to automatically derive a safe approximation of the semantics of the original program. The approach is flexible in the sense that the first phase decouples the analyzer from most language-dependent features, and correct because the set of Horn clauses returned by the transformation phase safely approximates the standard semantics of the input program. The resulting analysis is also reasonably scalable due to the use of mature, modular (C)LP-based analyzers. This allows us to report good results for medium-sized programs.
41412953
BoogiePL: A typed procedural language for checking object-oriented programs
This note defines BoogiePL, an intermediate language for program analysis and program verification. The language is a simple coarsely typed imperative language with procedures and arrays, plus support for introducing mathematical functions and declaring properties of these functions. BoogiePL can be used to represent programs written in an imperative source language (like an object-oriented .NET language), along with a logical encoding of the semantics of such a source language. From the resulting BoogiePL program, one can then generate verification conditions or perform other program analyses such as the inference of program invariants. In this way, BoogiePL also serves as a programming-notation front end to theorem provers. BoogiePL is accepted as input to Boogie, the Spec# static program verifier.
5223577
Using Datalog with Binary Decision Diagrams for Program Analysis
Many problems in program analysis can be expressed naturally and concisely in a declarative language like Datalog. This makes it easy to specify new analyses or extend or compose existing analyses. However, previous implementations of declarative languages perform poorly compared with traditional implementations. This paper describes bddbddb, a BDD-Based Deductive DataBase, which implements the declarative language Datalog with stratified negation, totally-ordered finite domains and comparison operators. bddbddb uses binary decision diagrams (BDDs) to efficiently represent large relations. BDD operations take time proportional to the size of the data structure, not the number of tuples in a relation, which leads to fast execution times. bddbddb is an effective tool for implementing a large class of program analyses. We show that a context-insensitive points-to analysis implemented with bddbddb is about twice as fast as a carefully hand-tuned version. The use of BDDs also allows us to solve heretofore unsolved problems, like context-sensitive pointer analysis for large programs.
9907339
Abstract Interpretation of PIC Programs through Logic Programming
A logic based general approach to abstract interpretation of low-level machine programs is reported. It is based on modelling the behavior of the machine as a logic program. General purpose program analysis and transformation of logic programs, such as partial evaluation and convex hull analysis, are applied to the logic based model of the machine. A small PIC microcontroller is used as a case study. An emulator for this microcontroller is written in Prolog, and standard programming transformations and analysis techniques are used to specialise this emulator with respect to a given PIC program. The specialised emulator can now be further analysed to gain insight into the given program for the PIC microcontroller. The method describes a general framework for applying abstractions, illustrated here by linear constraints and convex hull analysis, to logic programs. Using these techniques on the specialised PIC emulator, it is possible to obtain constraints on and linear relations between data registers, enabling detection of for instance overflows, branch conditions and so on.
3265044
Verification of Java Bytecode Using Analysis and Transformation of Logic Programs
State of the art analyzers in the Logic Programming (LP) paradigm are nowadays mature and sophisticated. They allow inferring a wide variety of global properties including termination, bounds on resource consumption, etc. The aim of this work is to automatically transfer the power of such analysis tools for LP to the analysis and verification of Java bytecode (jvml). In order to achieve our goal, we rely on well-known techniques for meta-programming and program specialization. More precisely, we propose to partially evaluate a jvml interpreter implemented in LP together with (an LP representation of) a jvml program and then analyze the residual program. Interestingly, at least for the examples we have studied, our approach produces very simple LP representations of the original jvml programs. This can be seen as a decompilation from jvml to high-level LP source. By reasoning about such residual programs, we can automatically prove in the CiaoPP system some non-trivial properties of jvml programs such as termination, run-time error freeness and infer bounds on its resource consumption. We are not aware of any other system which is able to verify such advanced properties of Java bytecode.
54117279
The Coq proof assistant : reference manual, version 6.1
Coq is a proof assistant based on a higher-order logic allowing powerful definitions of functions. Coq V6.1 is available by anonymous ftp at ftp.inria.fr:/INRIA/Projects/coq/V6.1 and ftp.ens-lyon.fr:/pub/LIP/COQ/V6.1
9187689
Specialising Interpreters Using Offline Partial Deduction
We present the latest version of the {\sc logen} partial evaluation system for logic programs. In particular we present new binding-types, and show how they can be used to effectively specialise a wide variety of interpreters.We show how to achieve Jones-optimality in a systematic way for several interpreters. Finally, we present and specialise a non-trivial interpreter for a small functional programming language. Experimental results are also presented, highlighting that the {\sc logen} system can be a good basis for generating compilers for high-level languages.
9140298
Type-Based Homeomorphic Embedding and Its Applications to Online Partial Evaluation
Homeomorphic Embedding( HEm ) has proven to be very powerful for supervising termination of computations, provided that such computations are performed over a finite signature, i.e., the number of constants and function symbols involved is finite. However, there are situations, for example numeric computations, which involve an infinite (or too large) signature, in which HEm does not guarantee termination. Some extensions to HEm for the case of infinite signatures have been proposed which guarantee termination, but they either do not provide systematic means for generating such extensions or the extensions are too simplistic and do not produce the expected results in practice. We introduce Type-based Homeomorphic Embedding( TbHEm ) as an extension of the standard, untyped HEm to deal with infinite signatures. In the paper, we show how TbHEm can be used to improve the accuracy of online partial evaluation. For this purpose, we propose an approach to constructing suitable types for partial evaluation automatically based on existing analysis tools for constraint logic programs. We also present useful properties of types which allow us to take full advantage of TbHEm in practice. Experimental results are reported which show that our work improves the state of the practice of online partial evaluation.
14968918
Tutorial on specialisation of logic programs
In this tutorial the specialisation of declarative logic programs is presented. The main correctness results are given, and the outline of a basic algorithm for partial evaluation of a logic program with respect to a goal. The practical considerations of gaining efficiency (and not losing any) are discussed. A renaming scheme for performing structure specialisation is then described, and illustrated on a well-known string matching example. The basic algorithm is enhanced by incorporating abstract interpretation. A two-phase specialisation is then described and illustrated, in which partial evaluation is followed by the detection and removal of useless clauses. This is shown for the specialisation of a proof procedure for first order logic. The specialisation of meta programs is very important in logic programming, and the ground representation for object programs has to be handled. Some techniques for doing this are described. Comparisons are made in the tutorial to similar work in other programming languages, and the similarities and differences between them and logic program specialisation is discussed.
10353113
Homeomorphic Embedding for Online Termination of Symbolic Methods
Well-quasi orders in general, and homeomorphic embedding in particular, have gained popularity to ensure the termination of techniques for program analysis, specialisation, transformation, and verification. In this paper we survey and discuss this use of homeomorphic embedding and clarify the advantages of such an approach over one using well-founded orders. We also discuss various extensions of the homeomorphic embedding relation. We conclude with a study of homeomorphic embedding in the context of metaprogramming, presenting some new (positive and negative) results and open problems.
37939195
Partial Evaluation in Logic Programming
Abstract This paper gives a theoretical foundation for partial evaluation in logic programming. Let P be a normal program, G a normal goal, A a finite set of atoms, and P ′ a partial evaluation of P wrt A . We study, for both the declarative and procedural semantics, conditions under which P ′ is sound and complete wrt P for the goal G . We identify two relevant conditions, those of closedness and independence. For the procedural semantics, we show that, if P ′ ∪ { G } is A -closed and A is independent, then P ′ is sound and complete wrt P for the goal G . For the declarative semantics, we show that, if P ′ ∪ { G } is A -closed, then P ′ is sound wrt P for the goal G . However, we show that, unless strong conditions are imposed, we do not have completeness for the declarative semantics. A practical consequence of our results is that partial evaluators should enforce the closedness and independence conditions.
14354009
Redundant Argument Filtering of Logic Programs
This paper is concerned with the problem of removing redundant arguments from logic programs. Such arguments can be removed without affecting correctness, in a certain sense. Most program specialisation techniques, even though they filter arguments and remove clauses, fail to remove a substantial number of redundant arguments, yielding in some cases rather inefficient residual programs. We formalise the notion of a redundant argument and show that one cannot effectively remove all redundant arguments. We then give a safe, effective approximation of the notion of a redundant argument and describe several simple and efficient algorithms based on the approximative notion. We conduct extensive experiments with our algorithms on mechanically generated programs illustrating the practical benefits of our approach.
13297768
Non-leftmost Unfolding in Partial Evaluation of Logic Programs with Impure Predicates
Partial evaluation of logic programs which contain impure predicates poses non-trivial challenges. Impure predicates include those which produce side-effects, raise errors (or exceptions), and those whose truth value varies according to the degree of instantiation of arguments. In particular, non-leftmost unfolding steps can produce incorrect results since the independence of the computation rule no longer holds in the presence of impure predicates. Existing proposals allow non-leftmost unfolding steps, but at the cost of accuracy: bindings and failure are not propagated backwards to predicates which are potentially impure. In this work we propose a partial evaluation scheme which substantially reduces the situations in which such backpropagation has to be avoided. With this aim, our partial evaluator takes into account the information about purity of predicates expressed in terms of assertions. This allows some optimizations which are not feasible using existing partial evaluation techniques. We argue that our proposal goes beyond existing ones in that it is a) accurate, since the classification of pure vs impure is done at the level of atoms instead of predicates, b) extensible, as the information about purity can be added to programs using assertions without having to modify the partial evaluator itself, and c) automatic, since (backwards) analysis can be used to automatically infer the required assertions. Our approach has been implemented in the context of CiaoPP, the abstract interpretation-based preprocessor of the Ciao logic programming system.
14945994
A natural semantics for lazy evaluation
We define an operational semantics for lazy evaluation which provides an accurate model for sharing. The only computational structure we introduce is a set of bindings which corresponds closely to a heap. The semantics is set at a considerably higher level of abstraction than operational semantics for particular abstract machines, so is more suitable for a variety of proofs. Furthermore, because a heap is explicitly modelled, the semantics provides a suitable framework for studies about space behaviour of terms under lazy evaluation.
62596310
Using Regular Approximations for Generalisation During Partial Evalution
On-line partial evaluation algorithms include a generalisation step, which is needed to ensure termination. In partial evaluation of logic and functional programs, the usual generalisation operation applied to computation states is the most specific generalisation (msg) of expressions. This can cause loss of information, which is especially serious in programs whose computations first build some internal data structure, which is then used to control a subsequent phase of execution - a common pattern of computation. If the size of the intermediate data is unbounded at partial evaluation time then the msg will lose almost all information about its structure. Hence the second phase of computation cannot be effectively specialised. In this paper a generalisation based on regular approximations is presented. Regular approximations are recursive descriptions of term structure closely related to tree automata. A regular approximation of computation states can be built during partial evaluation. The critical point is that when generalisation is performed, the upper bound on regular descriptions can be combined with the msg, thus preserving structural information including recursively defined structure. The domain of regular approximations is infinite and hence a widening is incorporated in the generalisation to ensure termination. An algorithm for partial evaluation of logic programs, enhanced with regular approximations, along with some examples of its use will be presented.
5790731
Ecient Specialisation in Prolog Using a Hand-Written Compiler Generator
The so called “cogen approach” to program specialisation, writing a compiler generator instead of a specialiser, has been used with considerable success in partial evaluation of both functional and imperative languages. This paper demonstrates that this approach is also applicable to partial evaluation of logic programming languages, also called partial deduction. Self-application has not been as much in focus in logic programming as for functional and imperative languages, and the attempts to self-apply partial deduction systems have, of yet, not been altogether that successful. So, especially for partial deduction, the cogen approach should prove to have a considerable importance when it comes to practical applications. This paper first develops a generic offline partial deduction technique for pure logic programs, notably supporting partially instantiated datastructures via binding types. From this a very efficient cogen is derived, which generates very efficient generating extensions (executing up to several orders of magnitude faster than current online systems) which in turn perform very good and non-trivial specialisation, even rivalling existing online systems. All this is supported by extensive benchmarks. Finally, it is shown how the cogen can be extended to directly support a large part of Prolog’s declarative and non-declarative features and how semi-online specialisation can be efficiently integrated.
10578758
Efficient Local Unfolding with Ancestor Stacks for Full Prolog
The integration of powerful partial evaluation methods into practical compilers for logic programs is still far from reality. This is related both to 1) efficiency issues and to 2) the complications of dealing with practical programs. Regarding efficiency, the most successful unfolding rules used nowadays are based on structural orders applied over (covering) ancestors, i.e., a subsequence of the atoms selected during a derivation. Unfortunately, maintaining the structure of the ancestor relation during unfolding introduces significant overhead. We propose an efficient, practical local unfolding rule based on the notion of covering ancestors which can be used in combination with any structural order and allows a stack-based implementation without losing any opportunities for specialization. Regarding the second issue, we propose assertion-based techniques which allow our approach to deal with real programs that include (Prolog) built-ins and external predicates in a very extensible manner. Finally, we report on our implementation of these techniques in a practical partial evaluator, embedded in a state of the art compiler which uses global analysis extensively (the Ciao compiler and, specifically, its preprocessor CiaoPP). The performance analysis of the resulting system shows that our techniques, in addition to dealing with practical programs, are also significantly more efficient in time and somewhat more efficient in memory than traditional tree-based implementations.
7619774
Integrated program debugging, verification, and optimization using abstract interpretation (and the Ciao system preprocessor)
The technique of Abstract Interpretation has allowed the development of very sophisticated global program analyses which are at the same time provably correct and practical. We present in a tutorial fashion a novel program development framework which uses abstract interpretation as a fundamental tool. The framework uses modular, incremental abstract interpretation to obtain information about the program. This information is used to validate programs, to detect bugs with respect to partial specifications written using assertions (in the program itself and/or in system libraries), to generate and simplify run-time tests, and to perform high-level program transformations such as multiple abstract specialization, parallelization, and resource usage control, all in a provably correct way. In the case of validation and debugging, the assertions can refer to a variety of program points such as procedure entry, procedure exit, points within procedures, or global computations. The system can reason with much richer information than, for example, traditional types. This includes data structure shape (including pointer sharing), bounds on data structure sizes, and other operational variable instantiation properties, as well as procedure-level properties such as determinacy, termination, nonfailure, and bounds on resource consumption (time or space cost). CiaoPP, the preprocessor of the Ciao multi-paradigm programming system, which implements the described functionality, will be used to illustrate the fundamental ideas.
16615115
COSTA: Design and Implementation of a Cost and Termination Analyzer for Java Bytecode
This paper describes the architecture of costa , an abstract interpretation based cos t and t ermination a nalyzer for Java bytecode. The system receives as input a bytecode program, (a choice of) a resource of interest and tries to obtain an upper bound of the resource consumption of the program. costa provides several non-trivial notions of cost, as the consumption of the heap, the number of bytecode instructions executed and the number of calls to a specific method. Additionally, costa tries to prove termination of the bytecode program which implies the boundedness of any resource consumption. Having cost and termination together is interesting, as both analyses share most of the machinery to, respectively, infer cost upper bounds and to prove that the execution length is always finite (i.e., the program terminates). We report on experimental results which show that costa can deal with programs of realistic size and complexity, including programs which use Java libraries. To the best of our knowledge, this system provides for the first time evidence that resource usage analysis can be applied to a realistic object-oriented, bytecode programming language.
12983597
Supervising Offline Partial Evaluation of Logic Programs Using Online Techniques
A major impediment for more widespread use of offline partial evaluation is the difficulty of obtaining and maintaining annotations for larger, realistic programs. Existing automatic binding-time analyses still only have limited applicability and annotations often have to be created or improved and maintained by hand, leading to errors. We present a technique to help overcome this problem by using online control techniques which supervise the specialisation process in order to detect such errors. We discuss an implementation in the LOGEN system and show on a series of examples that this approach is effective: very few false alarms were raised while infinite loops were detected quickly. We also present the integration of this technique into a web interface, which highlights problematic annotations directly in the source code. A method to automatically fix incorrect annotations is presented, allowing the approach to be also used as a pragmatic binding time analysis. Finally we show how our method can be used for efficiently locating errors with builtins inside Prolog source code.
6733737
Programming Research Group Decompilation: the Enumeration of Types and Grammars Decompilation: the Enumeration of Types and Grammars
A free type deenition may be remolded into a simple functional program which enumerates all the terms of the associated grammar. This is the starting point for a reliable method of compiling decompilers. The technique produces eecient functional code and handles quite general synthetic and inherited attribute grammar descriptions (which correspond loosely to algebraically constrained and parametrized types in the functional programming terminology). Its eeciency derives from a close relationship between functionality and notation, and may also suggest a natural way to extend the popular list comprehension syntax. The theory developed here guarantees the correct-ness of a decompiler for an occam-like language, and, via a known correspondence between attribute grammars and logic programs, of a corresponding Prolog decompiler. Whilst enumerating grammars completely may be Halting Problem hard in general , it is shown here, with the aid of methods of abstract interpretation, that most grammars can be enumerated by the technique presented.
8229401
Decompilation of binary programs
The structure of a decompiler is presented, along with a thorough description of the different modules that form part of a decompiler, and the type of analyses that are performed on the machine code to regenerate high‐level language code. The phases of the decompiler have been grouped into three main modules: front‐end, universal decompiling machine, and back‐end. The front‐end is a machine‐dependent module that performs the loading, parsing and semantic analysis of the input program, as well as generating an intermediate representation of the program. The universal decompiling machine is a machine‐ and language‐independent module that performs data and control flow analysis of the program based on the intermediate representation, and the program's control flow graph. The back‐end is a language‐dependent module that deals with the details of the target high‐level language.
16227718
Disassembly of executable code revisited
Machine code disassembly routines form a fundamental component of software systems that statically analyze or modify executable programs, e.g., reverse engineering systems, static binary translators, and link-time optimizers. The task of disassembly is complicated by indirect jumps and the presence of non-executable data - jump tables, alignment bytes, etc. - in the instruction stream. Existing disassembly algorithms are not always able to cope successfully with executable files containing such features, and they fail silently - i.e., produce incorrect disassemblies without any indication that the results they are producing are incorrect. In this paper we examine two commonly-used disassembly algorithms and illustrate their shortcomings. We propose a hybrid approach that performs better than these algorithms in the sense that it is able to detect situations where the disassembly may be incorrect and limit the extent of such disassembly errors. Experimental results indicate that the algorithm is quite effective: the amount of code flagged as incurring disassembly errors is usually quite small.
13524695
Assembly to high-level language translation
Translation of assembly code to high-level language code is of importance in the maintenance of legacy code, as well as in the areas of program understanding, porting, and recovery of code. We present techniques used in the asm2c translator, a SPARC assembly to C translator. The techniques involve data and control flow analyses. The data flow analysis eliminates machine dependencies from the assembly code and recovers high-level language expressions. The control flow analysis recovers control structure statements. Simple data type recovery is also done. The presented techniques are extensions and improvements on previously developed CISC techniques. The choice of intermediate representation allows for both RISC and CISC assembly code to be supported by the analyses. We tested asm2c against SPEC95 SPARC assembly programs generated by a C compiler. Results using both unoptimized and optimized assembly code are presented.
1265256
Java Bytecode Verification: Algorithms and Formalizations
Bytecode verification is a crucial security component for Java applets, on the Web and on embedded devices such as smart cards. This paper reviews the various bytecode verification algorithms that have been proposed, recasts them in a common framework of dataflow analysis, and surveys the use of proof assistants to specify bytecode verification and prove its correctness.
206628735
Decompiling Java Bytecode: Problems, Traps and Pitfalls
Java virtual machines execute Java bytecode instructions. Since this bytecode is a higher level representation than traditional object code, it is possible to decompile it back to Java source. Many such decompilers have been developed and the conventional wisdom is that decompiling Java bytecode is relatively simple. This may be true when decompiling bytecode produced directly from a specific compiler, most often Sun's javac compiler. In this case it is really a matter of inverting a known compilation strategy. However, there are many problems, traps and pitfalls when decompiling arbitrary verifiable Java bytecode. Such bytecode could be produced by other Java compilers, Java byte-code optimizers or Java bytecode obfuscators. Java bytecode can also be produced by compilers for other languages, including Haskell, Eiffel, ML, Ada and Fortran. These compilers often use very different code generation strategies from javac.This paper outlines the problems and solutions we have found in our development of Dava, a decompiler for arbitrary Java bytecode. We first outline the problems in assigning types to variables and literals, and the problems due to expression evaluation on the Java stack. Then, we look at finding structured control flow with a particular emphasis on issues related to Java exceptions and synchronized blocks. Throughout the paper we provide small examples which are not properly decompiled by commonly used decompilers.
17759588
Software unit test coverage and adequacy
Objective measurement of test quality is one of the key issues in software testing. It has been a major research focus for the last two decades. Many test criteria have been proposed and studied for this purpose. Various kinds of rationales have been presented in support of one criterion or another. We survey the research work in this area. The notion of adequacy criteria is examined together with its role in software dynamic testing. A review of criteria classification is followed by a summary of the methods for comparison and assessment of criteria.
2940045
A System to Generate Test Data and Symbolically Execute Programs
This paper describes a system that attempts to generate test data for programs written in ANSI Fortran. Given a path, the system symbolically executes the path and creates a set of constraints on the program's input variables. If the set of constraints is linear, linear programming techniques are employed to obtain a solution. A solution to the set of constraints is test data that will drive execution down the given path. If it can be determined that the set of constraints is inconsistent, then the given path is shown to be nonexecutable. To increase the chance of detecting some of the more common programming errors, artificial constraints are temporarily created that simulate error conditions and then an attempt is made to solve each augmented set of constraints. A symbolic representation of the program's output variables in terms of the program's input variables is also created. The symbolic representation is in a human readable form that facilitates error detection as well as being a possible aid in assertion generation and automatic program documentation.
7887634
ATGen: automatic test data generation using constraint logic programming and symbolic execution †
The verification and validation of software through dynamic testing is an area of software engineering where progress towards automation has been slow. In particular the automatic design and generation of test data remains, by and large, a manual activity. This is despite the high promises that the symbolic execution technique engendered when it was first proposed as a method for automatic test data generation. This paper presents an automatic test data generator based on constraint logic programming and symbolic execution. After reviewing the symbolic execution technique, approaches for the resolution of the technical difficulties that have so far prevented symbolic execution from reaching its full potential in the area of automatic test data generation are presented. ATGen, an automatic test data generator, based on symbolic execution and that uses constraint logic programming, is then discussed. Copyright © 2001 John Wiley & Sons, Ltd.
2459781
A symbolic Java virtual machine for test case generation
Quality management is becoming a more and more important part of the software development process. As software testing is currently understood as the core function of the quality managment, developers start using software testing tools to facilitate their work. However most existing tools just manage given sets of test cases and check them against pre-defined testing criteria. The necessary test case discovery is usually up to user, who has to generate the test cases in an ad-hoc approach with only minimal support from the software. GlassTT, the tool we present in this paper, faces this problem by creating the needed test cases for a given criterion for a Java class file. It uses a symbolic Java virtual machine to generate constraints representing the conditions for the control flow under consideration. The system can employ a parameterizeable test criterion such as data-flow coverage. The constraint solvers embedded in the tool are capable of solving linear and non-linear constraints, which is sufficient for almost all constraints encountered in the execution of Java programs. They are encapsulated in an incremental constraint solver manager, which dynamically chooses an appropriate constraint solver and enables the efficient communication between constraint solvers and symbolical virtual machine.
9983849
Symbolic execution and program testing
This paper describes the symbolic execution of programs. Instead of supplying the normal inputs to a program (e.g. numbers) one supplies symbols representing arbitrary values. The execution proceeds as in a normal execution except that values may be symbolic formulas over the input symbols. The difficult, yet interesting issues arise during the symbolic execution of conditional branch type statements. A particular system called EFFIGY which provides symbolic execution for program testing and debugging is also described. It interpretively executes programs written in a simple PL/I style programming language. It includes many standard debugging features, the ability to manage and to prove things about symbolic expressions, a simple program testing manager, and a program verifier. A brief discussion of the relationship between symbolic execution and program proving is also included.