Non-termination checking for imperative programs to download

Pdf we present a static analysis technique for nontermination inference of logic programs. Termination and nontermination specification inference acm. We present an approach to automatic nontermination. Load the identifier x from the store and push it on the stack. Functional programming one feature that imperative programs lack is that they. Functional, declarative, and imperative programming.

Nontermination checking for imperative programs core. We present an approach to automatic nontermination checking that relates to termination checking in the same way as symbolic testing does to program verification. Lists are 3 een algoritme moet zo min mogelijk tijd in beslag nemen. In computer science, termination analysis is program analysis which attempts to determine. Pldi seeks outstanding research that has broad appeal and spans the breadth of programming languages. Of these, 38 projects have received substantial updates and 19 entries are completely new. Another use is to test whether an application does not hang in the presence of nontermination. Imperative programming encyclopedia of life support systems. Verified model checking of timed automata simon wimmer and peter lammich. Dec 01, 2009 experiments with nontermination analysis for java bytecode a. Termination analysis of higherorder functional programs. Us2005454a1 us12393,500 us39350009a us205454a1 us 2005454 a1 us2005454 a1 us 2005454a1 us 39350009 a us39350009 a us 39350009a us 205454 a1 us205454 a1 us 205454a1 authority us united states prior art keywords path program method conflict set prior art date 20080707 legal status the legal status is an assumption and is. Oct, 2009 we propose a program analysis method for proving termination of recursive programs.

Its not just that there is more, its that there is everything. This book constitutes the refereed proceedings of the 24th international conference on computer aided verification, cav 2012, held in berkeley, ca, usa in july 2012. Null, on the other hand exists, as a genuine real but unusual exceptional unexpected value. The halting problem which were talking about here is actually easily generalizable into a set of generic theorems about static analysis of programs in general. Citeseerx document details isaac councill, lee giles, pradeep teregowda. Declarative programming means any style of programming where your program is a description either of the problem or the solution but doesnt explicitly state how the work. While termination checking tailored to realworld library code or frameworks has received everincreasing attention during the last years, the complementary question of disproving termination properties as a means of debugging has largely been ignored so far. Our method is based on the automated generation of invariants that show that terminating states of a program are unreachable from certain initial states. Many meta programming systems process abstract syntax trees, but this requires intimate knowledge of the structure of the data type describing the abstract. The termination analysis is even more difficult than the halting problem. Cost of option some vs null the scala programming language. This paper discusses how to ensure confidentiality for multithreaded programs through a property called observational determinism.

Only a few recent papers address the problem of proving nontermination of imperative programs. Non termination checking for imperative programs paper in proceedings, 2008 while termination checking tailored to realworld library code or frameworks has received everincreasing attention during the last years, the complementary question of disproving termination properties as a means of debugging has largely been ignored so far. The sizechange termination principle for a rstorder functional language with wellfounded data is. A resourcebased logic for nontermination proofs automated. Another problem is nontermination of inference by backward chaining. We present an approach to automatic non termination checking that relates to termination checking in the same way as symbolic testing does to. Haskell has indeed evolved continuously since its original publication. Pldis emphases include innovative and creative approaches to compiletime and runtime technology, novel language designs and features, and. This is the 33rd edition of the haskell communities and activities report. All of the example programs used in this talk are available for download.

Initial work focused on generating test sets with better basic block coverage, not necessarily proving satisfiability of program assertions. In practice one fails to show termination or nontermination because every. Pdf nontermination inference of logic programs researchgate. The termination property is very sensitive to clause orderings. But youre correct, a term of type nat is indeed an ml program of type nat with various side effects, including non termination. Our tutorial presentation treats annotated programs formally, and provides a uniform development of vcgen algorithms from program logics. Our contribution is a novel type system in which the types are used to express and verify conditional safety, termination, nonsafety, and nontermination. The goal of pl1 is to be a comprehensive system modeling language and programming language. Dependent types for imperative programs aleksandar nanevski. Infinite looping problems that keep student programs from terminating may occur in many kinds of programming assignments. By comprehensive, we mean taking into account all components of the system, including application, database, and infrastructure, and taking into account all processes of the system, including development, maintenance, and deployment. Automatic nontermination analysis of imperative programs.

We give an empirical evaluation of the approach using a collection of nonterminating example programs topics. Most part of this work is devoted to automated static analyses that find recurrent sets in imperative programs. If we find a nonempty recurrent set and are able to show its reachability from an initial state then we prove the existence of a nonterminating execution. Type checking ensures to a high degree that the programmer does not ac.

Tests and proofs second international conference, tap. Haskelldenotational semantics wikibooks, open books for an. Contents 1 introduction 8 2 states and commands 11 2. We present an approach to automatic nontermination checking that relates to termination checking in the same way as symbolic. Automatic nontermination analysis of imperative programs helga velroyen diploma thesis in computer science rwth aachen university research group computer science ii programming languages and veri.

Coq already includes a powerful functional language that supports dependent types, but that language is limited to pure, total functions. Verification conditions for sourcelevel imperative programs. Plume research deals with methods for the formal analysis of computer programs and, more generally, of computing systems. Experiments with nontermination analysis for java bytecode. I get that being able to check for nontermination would be usefulbut is there more. We give an empirical evaluation of the approach using a. We present an approach to automatic nontermination checking that relates to termination checking in the same way as symbolic testing does to. Imperative programming means any style of programming where your program is structured out of instructions describing how the operations performed by a computer will happen. We reached the conclusion that nontermination is just, well, nontermination.

Active property checking extends the concept of checking properties at runtime on a dynamic symbolic execution of the program by combining it with constraint solving and test generation in order to further check using a new test input whether a property is actually violated as predicted by a prior imperfect symbolic execution. A recurrent set acts as a part of a nontermination proof. Cot5315 foundations of programming languages and software systems. We propose a unified logical framework for specifying and proving both termination and nontermination of various programs.

Nontermination checking for imperative programs of philipp. Termination check is very important in dependently typed programming. Functional programming in clean draft september 2, 2002. Software which runs into an infinite loop and thus does not terminate can become a serious problem in reallife software systems. If youre checking for null, then i guess youre going to have a. This covers the foundations of or of aspects of programming languages, and static analysis of programs.

We illustrate the utility of our nontermination prover, called tnt, on several nontrivial examples, some of which require bitlevel. We make anant available for download along with its source code at the fol. Our case study is a simple imperative programming language called imp. We give an empirical eval uation of the approach using a. The method is fully implemented on top of a program verification system and available for download. This algorithm uses invariants to prove the nontermination of the target program. In this paper, we propose a novel mechanism that analyzes and proves both program termination and non termination at the same time. Even though i find it exciting, i apologize if i may not continue. The analysis is based on a reduction of termination to two separate problems. This paper is a study of verification conditions for imperative, sequential, highlevel programming languages.

We present an approach to automatic non termination checking that relates to termination checking in the same way as symbolic testing does to program verification. This application relates to methods for program verification through symbolic enumeration of control path programs. Tap was the second conference devoted to the convergence of proofs and tests. This has a major impact on the scientific goals of plume, with a strong new direction on proof theory. We propose a program analysis method for proving termination of recursive programs. As described herein, such a check can be performed on a dynamic symbolic execution of a given program path using a constraint solver. In other words, active property checking extends runtime checking by checking whether a property is satisfied by all program executions that follow the same program path. So everything is machine checked and there are no gaps.

Computer aided verification 24th international conference. We can now use a safety checker to search for paths that violate this assertion. I could not have asked for a better supervisor, and cannot thank oege enough for his. Sep 2, 2002 a sequence of numbers can be put into a list in clean. Our framework is based on a resource logic which captures both upper and lower bounds on resources used by the programs. In this paper, we propose a novel mechanism that analyzes and proves both program termination and nontermination at the same time. Secure information flow is intended to maintain the confidentiality of sensitive information by preventing them from flowing to attackers. I meant that values of type nat in ml are always normalized whereas in haskell they may be considered programs of type nat.

Nontermination checking for imperative programs paper in proceedings, 2008 while termination checking tailored to realworld library code or frameworks has received everincreasing attention during the last years, the complementary question of disproving termination properties as a means of debugging has largely been ignored so far. Efficient verification of imperative programs using auto2 bohua zhan. Proving nontermination via safety ucl computer science. A read is counted each time someone views a publication summary such as the title, abstract, and list of authors, clicks on a figure, or views or downloads the fulltext. This paper considers verification of nondeterministic higherorder functional programs. Frame inference for inductive entailment proofs in separation logic quang loc le, jun sun and shengchao qin. A resourcebased logic for termination and nontermination proofs. Tests and proofs second international conference, tap 2008. Pldi is a premier forum for all areas of programming language research, including the design, implementation, theory, and efficient use of languages. Correct behavior in these systems may be specified in an operational or declarative style. Pldis emphases include innovative and creative approaches to compiletime and runtime technology, novel language designs and features. Declarative interpretations of sessionbased concurrency. Our new abstraction is supported by java and scheme libraries that allow programmers to use functional and oop techniques to develop traversal related.

Pdf nontermination checking for imperative programs. Techniques for proving termination and nontermination of imperative programs are usually considered as orthogonal mechanisms. While non terminating code is easier to diagnose interactively, it poses different concerns when software tests are being run automatically in batch. It should, formally speaking, be added to each type that needs one such value some dont, or forced on them by belonging to a. Proving nontermination proceedings of the 35th annual acm. Atkeys logic 6, a typebased amortized resource analysis for imperative programs. This volume contains the research papers, invited papers, and abstracts of torials presented at the second international conference on tests and proofs tap 2008 held april 911, 2008 in prato, italy. In this work we developed an algorithm to detect infinite loops in imperative programs. We propose a unified logical framework for specifying and proving both termination and non termination of various programs. The key contribution of our extension, which we call ynot, is the added support for computations that may have effects such as non termination, accessing a mutable store, and throwingcatching exceptions. Meta programming consists for a large part of matching, analyzing, and transforming syntax trees. By nontermination on compilation, i assume that you mean nontermination when evaluating the parser combinator expression during execution of the program, and not nontermination when compiling your program using parser combinators with mlton. Sessionbased concurrency is a typebased approach to the analysis of communicationintensive systems. The check that quasiinvariants can indeed be reached.

While nonterminating code is easier to diagnose interactively, it poses different concerns when software tests are being run automatically in batch. This report has 143 entries, many more than in the previous edition. Automatic nontermination analysis of imperative programs helga velroyen m. Preserving the confidentiality of information is a growing concern in software development. Techniques for proving termination and non termination of imperative programs are usually considered as orthogonal mechanisms.

Sound, complete, and tractable linearizability monitoring. Our reduction works through a program transformation that modifies the call sites and removes return edges. Haskelldenotational semantics wikibooks, open books for. By an abstraction, we evolve this resource logic for execution length into a temporal logic with three predicates to reason about termination. Mca free fulltext bisimulation for secure information. Loops in imperative programs can always be modeled by recursion in functional programs. Methods for proving nontermination of programs ucl computer. Nontermination checking for imperative programs springerlink. This sentence means that when a type system is so powerful that it can show every desired property of a program for example termination, then the type checking becomes undecidable, meaning that there will be programs for which the type checker will never be able to disprove a property even though the property does not hold for example that. Recurrent sets for nontermination and safety of programs.

The key contribution of our extension, which we call ynot, is the added support for computations that may have effects such as nontermination, accessing a mutable store, and throwingcatching exceptions. If the assemblies still dont show up, check rx is installed by checking add or remove programs in the control panel. Symbolic execution has been proposed as a method for generalizing dynamic testing. Nontermination checking for imperative programs citeseerx. Termination and nontermination specification inference. The only difference is that, when b evaluates to true, we execute c and check. Nontermination checking for imperative programs helga velroyen1 and philipp rumme.