Experimenting with Predicate Abstraction

Predicate abstraction is a technique employed in software model checking to produce abstract models that can be conservatively checked for property violations in reasonable time. The precision degree of different abstractions of the same program may differ based on (i) the set of predicates used; or (ii) the algorithmic technique employed to generate the model. In this report we explain how we have extended the implementation of one such technique, that produces the most precise ex- istential abstraction of a program, and we establish a common framework for both this direct technique and a second one, based on cartesian ab- straction by weakest precondition calculations. This report a product of the research grant BI22012 PTDC/EIA-CCO/117590/2010 UMINHO, in the scope of the AVIACC project, supervised by Professors Jorge Sousa Pinto and Maria João Frade.This work is funded by ERDF - European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the FCT - Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within project FCOMP-01-0124-FEDER-020486

SABS : Spark ABStraction - A Tutorial

SABS is a predicate abstraction laboratory that is beeing developed at University of Minho, Portugal. Our goal is not to produce a industrial software model checker, such as SLAM [BMR01] or SATABS [CKSY05], but to have a tool to study and compare the diferent techniques (and combination of techniques) that can be used to perform the predicate abstraction of a program, in our case, a SPARK program. This document is a both a tutorial on the usage of SABS and a (small) explanation of its implementation. Some knowledge on Predicate Abstraction and Program Verification is assumed, we refer the reader to [MLPF13] for some background on the techniques implemented by SABS.This work is funded by ERDF - European Regional Development Fund through the COMPETE Programme (operational programme for competitiveness) and by National Funds through the FCT - Fundação para a Ciência e a Tecnologia (Portuguese Foundation for Science and Technology) within project FCOMP-01-0124-FEDER-020486

SPARK-BMC: checking SPARK code for bugs

The standard SPARK deductive verification tools, based on contracts, are not practical in early stages when the idea is only bug catching. We discuss the implementation of a bounded model checker for SPARK, focusing on specific challenges of this language. Our tool is fully automatic, complementing the existing tools for SPARK.Fundação para a Ciência e a Tecnologia (FCT

Experimenting with predicate abstraction

Predicate abstraction is a technique employed in software model checking to produce abstract models that can be conservatively checked for property violations in reasonable time. The precision degree of different abstractions of the same program may differ based on (i) the set of predicates used; or (ii) the algorithmic technique employed to gen- erate the model. In this paper we explain how we have implemented and optimized one such technique, that produces the most precise existential abstraction of a program, and give the first steps towards establishing a common framework for both this direct technique and a second one, based on cartesian abstraction by weakest precondition calculations.Fundação para a Ciência e a Tecnologia (FCT

Type-Safe Generic Differencing of Mutually Recursive Families

The UNIX diff tool, which computes the differences between two files in terms of a set of copied lines, is widely used in software version control. The fixed lines-of-code granularity, however, is sometimes too coarse and obscures simple changes, i.e., renaming a single parameter triggers the whole line to be seen as changed. This dissertation explores techniques and implementations for detecting and reasoning about changes in a finer granularity

Type-Safe Generic Differencing of Mutually Recursive Families

The UNIX diff tool, which computes the differences between two files in terms of a set of copied lines, is widely used in software version control. The fixed lines-of-code granularity, however, is sometimes too coarse and obscures simple changes, i.e., renaming a single parameter triggers the whole line to be seen as changed. This dissertation explores techniques and implementations for detecting and reasoning about changes in a finer granularity

Structure-aware Version Control : A generic approach using Agda

Modern version control systems are largely based on the UNIX diff3 program for merging line-based edits on a given file. Unfortunately, this bias towards line-based edits does not work well for all file formats, which may lead to unnecessary conflicts. This paper describes a data type generic approach to version control that exploits a file’s structure to create more precise diff and merge algorithms. We prototype and prove properties of these algorithms using the dependently typed language Agda; Our ideas can be, nevertheless, be transcribed to Haskell yielding a more scalable implementation

Structure-aware Version Control: A generic approach using Agda

Modern version control systems are largely based on the UNIX diff3 program for merging line-based edits on a given file. Unfortunately, this bias towards line-based edits does not work well for all file formats, which may lead to unnecessary conflicts. This paper describes a data type generic approach to version control that exploits a file’s structure to create more precise diff and merge algorithms. We prototype and prove properties of these algorithms using the dependently typed language Agda; Our ideas can be, nevertheless, be transcribed to Haskell yielding a more scalable implementation