Automating C++ Execution Exploration to Solve the Out-of-thin-air Problem

Modern computers are marvels of engineering. Customisable reasoning engines which can be programmed to complete complex mathematical tasks at incredible speed. Decades of engineering has taken computers from room sized machines to near invisible devices in all aspects of life. With this engineering has come more complex and ornate design, a substantial leap forward being multiprocessing. Modern processors can execute threads of program logic in parallel, coordinating shared resources like memory and device access. Parallel computation leads to significant scaling of compute power, but yields a substantial complexity cost for both processors designers and programmers. Parallel access to shared memory requires coordination on which thread can use a particular fragment of memory at a given time. Simple mechanisms like locks and mutexes ensure only one process at a time can access memory gives an easy to use programming model, but they eschew the benefits of parallel computation. Instead, processors today have complex mechanisms to permit concurrent shared memory access. These mechanisms prevent simple programmer reasoning and require complex formal descriptions to define: memory models. Early memory model research focused on weak memory behaviours which are observable because of hardware design; over time it has become obvious that not only hardware but compilers are capable of making new weak behaviours observable. Substantial and rapid success has been achieved formalising the behaviour of these machines: researchers refined new specifications for shared-memory concurrency and used mechanisation to automate validation of their models. As the models were refined and new behaviours of the hardware were discovered, researchers also began working with processor vendors – helping to inform design choices in new processor designs to keep the weak behaviours within some sensible bounds. Unfortunately when reasoning about shared memory accesses of highly optimised programming languages like C and C++, deep questions are still left open about how best to describe the behaviour of shared memory accesses in the presence of dependency removing compiler optimisations. Until very recently it has not been possible to properly specify the behaviours of these programs without forbidding ii optimisations which are used and observable, or allowing program behaviours which are nonsense and never observable. In this thesis I explore the development of memory models through the lens of tooling: taking at first an industrial approach, and then exploring memory models for highly optimised programming languages. I show that taming the complexity of these models with automated tools aids bug finding even where formal evaluation has not. Further, building tools creates a focus on the computational complexity of the memory model which in turn can steer development of the model towards simpler designs. We will look at 3 case studies: the first is an industrial hardware model of NVIDIA GPUs which we extend to encompass more hardware features than before. This extension was validated using an automated testing process generating tests of finite size, and then verified against the original memory model in Coq. The second case study is an exploration of the first memory model for an optimised programming language which takes proper account of dependencies. We build a tool to automate execution of this model over a series of tests, and in the process discovered subtleties in the definitions which were unexpected – leading to refinement of the model. In the final case study, we develop a memory model that gives a direct definition for compiler preserved dependencies. This model is the first model that can be integrated with relative ease into the C/C++ programming language standard. We built this model alongside its own tooling, yielding a fast tool for giving determinations on a large number of litmus tests – a novelty for this sort of memory model. This model fits well with the existing C/C++ specifications, and we are working with the International Standards Organisation to understand how best to fit this model in the standard

Tools and Algorithms for the Construction and Analysis of Systems

This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems

Tools and Algorithms for the Construction and Analysis of Systems

This open access book constitutes the proceedings of the 28th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2022, which was held during April 2-7, 2022, in Munich, Germany, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2022. The 46 full papers and 4 short papers presented in this volume were carefully reviewed and selected from 159 submissions. The proceedings also contain 16 tool papers of the affiliated competition SV-Comp and 1 paper consisting of the competition report. TACAS is a forum for researchers, developers, and users interested in rigorously based tools and algorithms for the construction and analysis of systems. The conference aims to bridge the gaps between different communities with this common interest and to support them in their quest to improve the utility, reliability, exibility, and efficiency of tools and algorithms for building computer-controlled systems

Automated Deduction – CADE 28

This open access book constitutes the proceeding of the 28th International Conference on Automated Deduction, CADE 28, held virtually in July 2021. The 29 full papers and 7 system descriptions presented together with 2 invited papers were carefully reviewed and selected from 76 submissions. CADE is the major forum for the presentation of research in all aspects of automated deduction, including foundations, applications, implementations, and practical experience. The papers are organized in the following topics: Logical foundations; theory and principles; implementation and application; ATP and AI; and system descriptions

Tools and Algorithms for the Construction and Analysis of Systems

This open access two-volume set constitutes the proceedings of the 27th International Conference on Tools and Algorithms for the Construction and Analysis of Systems, TACAS 2021, which was held during March 27 – April 1, 2021, as part of the European Joint Conferences on Theory and Practice of Software, ETAPS 2021. The conference was planned to take place in Luxembourg and changed to an online format due to the COVID-19 pandemic. The total of 41 full papers presented in the proceedings was carefully reviewed and selected from 141 submissions. The volume also contains 7 tool papers; 6 Tool Demo papers, 9 SV-Comp Competition Papers. The papers are organized in topical sections as follows: Part I: Game Theory; SMT Verification; Probabilities; Timed Systems; Neural Networks; Analysis of Network Communication. Part II: Verification Techniques (not SMT); Case Studies; Proof Generation/Validation; Tool Papers; Tool Demo Papers; SV-Comp Tool Competition Papers

Efficient local search for Pseudo Boolean Optimization

Algorithms and the Foundations of Software technolog