Actris 2.0: Asynchronous Session-Type Based Reasoning in Separation Logic

Message passing is a useful abstraction for implementing concurrent programs. For real-world systems, however, it often combined with other programming and concurrency paradigms, such as higher-order functions, mutable state, shared-memory concurrency, locks. We present Actris: logic proving functional correctness of programs that use combination the aforementioned features. Actris combines power modern separation logics first-class protocol mechanism -- based on session types reasoning about message in presence paradigms. show provides suitable level by variety examples, including channel-based merge sort, load-balancing mapper, variant map-reduce model, using concise specifications. While was already presented conference paper (POPL'20), this expands prior presentation significantly. Moreover, extends to 2.0 notion subprotocols session-type subtyping permits additional flexibility when composing channel endpoints, takes full advantage asynchronous semantics Actris. Soundness proven model its Iris framework. have mechanised theory Actris, together custom tactics, well all examples paper, Coq proof assistant.