Unifying type checking and property checking for low-level code

  • Authors:

  • Jeremy Condit;Brian Hackett;Shuvendu K. Lahiri;Shaz Qadeer

  • Affiliations:

  • Microsoft Research, Redmond, WA, USA;Stanford University, Stanford, CA, USA;Microsoft Research, Redmond, WA, USA;Microsoft Research, Redmond, WA, USA

  • Venue:
  • Proceedings of the 36th annual ACM SIGPLAN-SIGACT symposium on Principles of programming languages
  • Year:
  • 2009

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Abstract

We present a unified approach to type checking and property checking for low-level code. Type checking for low-level code is challenging because type safety often depends on complex, program-specific invariants that are difficult for traditional type checkers to express. Conversely, property checking for low-level code is challenging because it is difficult to write concise specifications that distinguish between locations in an untyped program's heap. We address both problems simultaneously by implementing a type checker for low-level code as part of our property checker. We present a low-level formalization of a C program's heap and its types that can be checked with an SMT solver, and we provide a decision procedure for checking type safety. Our type system is flexible enough to support a combination of nominal and structural subtyping for C, on a per-structure basis. We discuss several case studies that demonstrate the ability of this tool to express and check complex type invariants in low-level C code, including several small Windows device drivers.