RPP: Automatic Proof of Relational Properties by Self-Composition

Self-composition provides a powerful theoretical approach to prove relational properties, i.e. properties relating several program executions, that has been applied to compare two runs of one or similar programs (in secure dataflow properties, code transformations, etc.). This tool demo paper presents RPP, an original implementation of self-composition for specification and verification of relational properties in C programs in the FRAMA-C platform. We consider a very general notion of relational properties invoking any finite number of function calls of possibly dissimilar functions with possible nested calls. The new tool allows the user to specify a relational property, to prove it in a completely automatic way using classic deductive verification, and to use it as a hypothesis in the proof of other properties that may rely on it

StaDy: Deep Integration of Static and Dynamic Analysis in Frama-C

We present StaDy, a new integration of the concolic test generator PathCrawler within the software analysis platform Frama- C. When executing a dynamic analysis of a C code, the integrated test generator also exploits its formal specification, written in an executable fragment of the acsl specification language shared with other analyzers of Frama-C. The test generator provides the user with accurate verdicts, that other Frama-C plugins can reuse to improve their own analyses. This tool is designed to be the foundation stone of static and dynamic analysis combinations in the Frama-C platform. Our first experiments confirm the benefits of such a deep integration of static and dynamic analysis within the same platform

Static versus Dynamic Verification in Why3, Frama-C and SPARK 2014

International audienceWhy3 is an environment for static verification, generic in the sense that it is used as an intermediate tool by different front-ends for the verification of Java, C or Ada programs. Yet, the choices made when designing the specification languages provided by those front-ends differ significantly, in particular with respect to the executability of specifications. We review these differences and the issues that result from these choices. We emphasize the specific feature of ghost code which turns out to be extremely useful for both static and dynamic verification. We also present techniques, combining static and dynamic features, that help users understand why static verification fails

Improving static analyses of C programs with conditional predicates

Extended version of the FMICS 2014 paperInternational audienceStatic code analysis is increasingly used to guarantee the absence of undesirable behaviors in industrial programs. Designing sound analyses is a continuing trade-off between precision and complexity. Notably, dataflow analyses often perform overly wide approximations when two control-flow paths meet, by merging states from each path.This paper presents a generic abstract interpretation based framework to enhance the precision of such analyses on join points. It relies on predicated domains, that preserve and reuse information valid only inside some branches of the code. Our predicates are derived from conditional statements, and postpone the loss of information.The work has been integrated into Frama-C, a C source code analysis platform. Experiments on real generated code show that our approach scales, and improves significantly the precision of the existing analyses of Frama-C

Improving static analyses of C programs with conditional predicates

Best paper awardInternational audienceStatic code analysis is increasingly used to guarantee the absence of undesirable behaviors in industrial programs. Designing sound analyses is a continuing trade-off between precision and complexity. Notably, dataflow analyses often perform overly wide approximations when two control-flow paths meet, by merging states from each path. This paper presents a generic abstract interpretation based framework to enhance the precision of such analyses on join points. It relies on predicated domains, that preserve and reuse information valid only inside some branches of the code. Our predicates are derived from conditionals statements, and postpone the loss of information. The work has been integrated into Frama-C, a C source code analysis platform. Experiments on real code show that our approach scales, and improves significantly the precision of the existing analyses of Frama-C

Combining Analyses for C Program Verification

International audienceStatic analyzers usually return partial results. They can assert that some properties are valid during all possible executions of a program, but generally leave some other properties to be verified by other means. In practice, it is common to combine results from several methods manually to achieve the full verification of a program. In this context, Frama-C is a platform for analyzing C source programs with multiple analyzers. Hence, one analyzer might conclude about properties assumed by another one, in the same environment. We present here the semantical foundations of validity of program properties in such a context. We propose a correct and complete algorithm for combining several partial results into a fully consolidated validity status for each program property. We illustrate how such a framework provides meaningful feedback on partial results