Mechanised Operational Reasoning for C11 Programs with Relaxed Dependencies

Verification techniques for C11 programs have advanced significantly in recent years with the development of operational semantics and associated logics for increasingly large fragments of C11. However, these semantics and logics have been developed in a restricted setting to avoid the thin-air-read problem. In this article, we propose an operational semantics that leverages an intra-thread partial order (called semantic dependencies) induced by a recently developed denotational event-structure-based semantics. We prove that our operational semantics is sound and complete with respect to the denotational semantics. We present an associated logic that generalises a recent Owicki–Gries framework for RC11 RAR (repaired C11) with relaxed and release-acquire accesses. We describe the mechanisation of the logic in the Isabelle/HOL theorem prover, which we use to prove correctness of a number of examples.