Inter-process buffers in separation logic with rely-guarantee

Separation logic allows simple proofs of concurrent algorithms which use blocking mechanisms such as semaphores. It can even deal with non-blocking algorithms. With the addition of mechanisms borrowed from rely-guarantee, we can make reasonably simple proofs of some simple non-blocking algorithms. We show that it extends to proofs of some intricate algorithms, including Simpson’s famous asynchronous four-slot buffer and Harris’s novel three-slot algorithm, in a manner that is arguably simpler than earlier treatments, though we cannot claim that we have yet found proofs that are as simple as we would wish. Our example proofs show functional correctness but do not deal with questions of liveness.