The research presented in this thesis concerns one of the most important questions in software engineering of our time: how can we make sure that software is free from memory safety bugs? Memory... Show moreThe research presented in this thesis concerns one of the most important questions in software engineering of our time: how can we make sure that software is free from memory safety bugs? Memory safety bugs are the major cause of common vulnerabilities and exposures, and their presence threatens the stability and security of our digital world. This question is so important that it has escalated to the highest level. In a recent White House press release (February 26, 2024), the National Cyber Director of the United States of America calls on the academic community to help solve this hard problem: “addressing [this challenge] is imperative to ensuring we can secure our digital ecosystem long-term and protect the security of our Nation.” The accompanying technical report advises on the use of memory safe programming languages, and prominently mentions formal methods as one way to achieve the highly desired freedom from bugs, including memory safety bugs.In this thesis, formal methods are studied that are used to analyze software for its correctness, where correctness means that software satisfies its specification and incorrectness means the presence of a bug. The focus is on separation logic, a formal method designed as a scalable technique in ensuring freedom from memory safety bugs. Nowadays, separation logic is a well-established field of research: it has been widely studied academically in the past twenty years, and is successfully applied on an industry-wide scale to ensure memory safety. For example, separation logic is the technique used to prove, with mathematical certainty, that memory safe programming languages (such as Rust and Go) indeed live up to the promise that “they offer a way to eliminate, not just mitigate, entire bug classes.”In two parts, this thesis presents important scientific contributions that fill a gap in the academic literature. The first part contains the missing completeness theorem for separation logic, that is on par with the fundamental result by Goedel for first-order logic. Completeness is important for any formal method as it shows that the formal method can be adequately used for demonstrating every validity. The second part finally introduces dynamic separation logic that gives an alternative way to analyze memory safety problems, such that now it is possible to prove elementary specifications without needing extra logical techniques. This is important because it ensures ‘backwards compatibility’ with automated reasoning techniques that are optimized for first-order logic. Show less
The development process of any software has become extremely important not just in the IT industry, but in almost every business or domain of research. The effort in making this process quick,... Show moreThe development process of any software has become extremely important not just in the IT industry, but in almost every business or domain of research. The effort in making this process quick, efficient, reliable and automated has constantly evolved into a flow that delivers software incrementally based on both the developer's best skills and the end user's feedback. Software modeling and modeling languages have the purpose of facilitating product development by designing correct and reliable applications. The concurrency model of the Abstract Behavioural Specification (ABS) Language with features for asynchronous programming and cooperative scheduling is an important example of how modeling contributes to the reliability and robustness of a product. By abstracting from the implementation details, program complexity and inner workings of libraries, software modeling, and specifically ABS, allow for an easier use of formal analysis techniques and proofs to support product design. However there is still a gap that exists between modeling languages and programming languages with the process of software development often going on two separate paths with respect to modeling and implementation. This potentially introduces errors and doubles the development effort. \par The overall objective of this research is bridging the gap between modeling and programming in order to provide a smooth integration between formal methods and two of the most well-known and used languages for software development, the Java and Scala languages. The research focuses mainly on sequential and highly parallelizable applications, but part of the research also involves some theoretical proposals for distributed systems. It is a first step towards having a programming language with support for formal models. Show less
The remainder of this thesis is organized as follows. Chapters 2 and 3 introduce the specification formalisms that are used in this thesis. In Chapter 2 we present the computation language. We show... Show moreThe remainder of this thesis is organized as follows. Chapters 2 and 3 introduce the specification formalisms that are used in this thesis. In Chapter 2 we present the computation language. We show that it facilitates the description of specifications that are not partial to a particular mode of execution. Furthermore, we present a semantics and a logic for reasoning about correctness of programs. In Chapter 3 we present the coordination language. We define its semantics and show how it connects to the computation language. In Chapters 4 and 5 we develop a theory of refinement. This theory provides a number of proof techniques that enable us to incrementally refine the behavioural aspects of a program. These chapters form the most theoretical part of this thesis. It should be possible to get an understanding of the methods derived in these chapters without going through all these proofs. In Chapter 7 we illustrate the method of design by considering some case studies. Comparisons with related work and conclusions are described in Chapters 8 and 9. Show less
