Correct-by-Construction Concurrency: Using Dependent Types to Verify Implementations of Effectful Resource Usage Protocols

  • Authors:
  • Edwin Brady;Kevin Hammond

  • Affiliations:
  • (Correspd.) School of Computer Science, University of St Andrews, Jack Cole Building, North Haugh, St Andrews, Fife KY16 9SX, United Kingdom. {eb,kh}@cs.st-andrews.ac.uk;School of Computer Science, University of St Andrews, Jack Cole Building, North Haugh, St Andrews, Fife KY16 9SX, United Kingdom. {eb,kh}@cs.st-andrews.ac.uk

  • Venue:
  • Fundamenta Informaticae - Dependently Typed Programming
  • Year:
  • 2010

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Abstract

In the modern, multi-threaded, multi-core programming environment, correctly managing system resources, including locks and shared variables, can be especially difficult and errorprone. A simple mistake, such as forgetting to release a lock, can have major consequences on the correct operation of a program, by, for example, inducing deadlock, often at a time and location that is isolated from the original error. In this paper, we propose a new type-based approach to resource management, based on the use of dependent types to construct a Domain-Specific Embedded Language (DSEL) whose typing rules directly enforce the formal program properties that we require. In this way, we ensure strong static guarantees of correctness-by-construction, without requiring the development of a new special-purpose type system or the associated special-purpose soundness proofs. We also reduce the need for “over-serialisation”, the overly-conservative use of locks that often occurs in manually constructed software, where formal guarantees cannot be exploited. We illustrate our approach by implementing a DSEL for concurrent programming and demonstrate its applicability with reference to an example based on simple bank account transactions.