Bertrand Meyer, Alisa Arkadova, Alexander Kogtenkov
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引用次数: 0
Abstract
Class invariants — consistency constraints preserved by every operation on objects of a given type — are fundamental to building, understanding and verifying object-oriented programs. For verification, however, they raise difficulties, which have not yet received a generally accepted solution. The present work introduces a proof rule meant to address these issues and allow verification tools to benefit from invariants.
It clarifies the notion of invariant and identifies the three associated problems: callbacks, furtive access and reference leak. As an example, the 2016 Ethereum DAO bug, in which $50 million were stolen, resulted from a callback invalidating an invariant.
The discussion starts with a simplified model of computation and an associated proof rule, demonstrating its soundness. It then removes one by one the three simplifying assumptions, each removal raising one of the three issues, and leading to a corresponding adaptation to the proof rule. The final version of the rule can tackle tricky examples, including “challenge problems” listed in the literature.
期刊介绍：
This journal aims to publish contributions at the junction of theory and practice. The objective is to disseminate applicable research. Thus new theoretical contributions are welcome where they are motivated by potential application; applications of existing formalisms are of interest if they show something novel about the approach or application.
In particular, the scope of Formal Aspects of Computing includes:
well-founded notations for the description of systems;
verifiable design methods;
elucidation of fundamental computational concepts;
approaches to fault-tolerant design;
theorem-proving support;
state-exploration tools;
formal underpinning of widely used notations and methods;
formal approaches to requirements analysis.
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