482 research outputs found
The Dafny Integrated Development Environment
In recent years, program verifiers and interactive theorem provers have
become more powerful and more suitable for verifying large programs or proofs.
This has demonstrated the need for improving the user experience of these tools
to increase productivity and to make them more accessible to non-experts. This
paper presents an integrated development environment for Dafny-a programming
language, verifier, and proof assistant-that addresses issues present in most
state-of-the-art verifiers: low responsiveness and lack of support for
understanding non-obvious verification failures. The paper demonstrates several
new features that move the state-of-the-art closer towards a verification
environment that can provide verification feedback as the user types and can
present more helpful information about the program or failed verifications in a
demand-driven and unobtrusive way.Comment: In Proceedings F-IDE 2014, arXiv:1404.578
Refinement with Time - Refining the Run-Time of Algorithms in Isabelle/HOL
Separation Logic with Time Credits is a well established method to formally verify the correctness and run-time of algorithms, which has been applied to various medium-sized use-cases. Refinement is a technique in program verification that makes software projects of larger scale manageable.
Combining these two techniques for the first time, we present a methodology for verifying the functional correctness and the run-time analysis of algorithms in a modular way. We use it to verify Kruskal\u27s minimum spanning tree algorithm and the Edmonds - Karp algorithm for network flow.
An adaptation of the Isabelle Refinement Framework [Lammich and Tuerk, 2012] enables us to specify the functional result and the run-time behaviour of abstract algorithms which can be refined to more concrete algorithms. From these, executable imperative code can be synthesized by an extension of the Sepref tool [Lammich, 2015], preserving correctness and the run-time bounds of the abstract algorithm
A Denotational Semantics for Communicating Unstructured Code
An important property of programming language semantics is that they should
be compositional. However, unstructured low-level code contains goto-like
commands making it hard to define a semantics that is compositional. In this
paper, we follow the ideas of Saabas and Uustalu to structure low-level code.
This gives us the possibility to define a compositional denotational semantics
based on least fixed points to allow for the use of inductive verification
methods. We capture the semantics of communication using finite traces similar
to the denotations of CSP. In addition, we examine properties of this semantics
and give an example that demonstrates reasoning about communication and jumps.
With this semantics, we lay the foundations for a proof calculus that captures
both, the semantics of unstructured low-level code and communication.Comment: In Proceedings FESCA 2015, arXiv:1503.0437
Generating Verified LLVM from Isabelle/HOL
We present a framework to generate verified LLVM programs from Isabelle/HOL. It is based on a code generator that generates LLVM text from a simplified fragment of LLVM, shallowly embedded into Isabelle/HOL. On top, we have developed a separation logic, a verification condition generator, and an LLVM backend to the Isabelle Refinement Framework.
As case studies, we have produced verified LLVM implementations of binary search and the Knuth-Morris-Pratt string search algorithm. These are one order of magnitude faster than the Standard-ML implementations produced with the original Refinement Framework, and on par with unverified C implementations. Adoption of the original correctness proofs to the new LLVM backend was straightforward.
The trusted code base of our approach is the shallow embedding of the LLVM fragment and the code generator, which is a pretty printer combined with some straightforward compilation steps
Fifty years of Hoare's Logic
We present a history of Hoare's logic.Comment: 79 pages. To appear in Formal Aspects of Computin
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