News
Release 4.2 – 2025-01-07
We are pleased to announce the release of Copilot 4.2, a stream-based DSL for writing and monitoring embedded C programs, with an emphasis on correctness and hard realtime requirements. Copilot is typically used as a high-level runtime verification framework, and supports temporal logic (LTL, PTLTL and MTL), clocks and voting algorithms.
Among others, Copilot is being used at the Safety Critical Avionics Systems Branch of NASA Langley Research Center for monitoring test flights of drones.
This release introduces several big improvements to Copilot:
Specifications can now use the same handler for multiple monitors, provided that the arguments to those handlers always have consistent types and arity. This simplifies the code that uses Copilot, since it’s no longer necessary to create multiple boilerplate wrappers around the same handling routines.
The use of structs has been vastly simplified. Before, it was necessary to define class instances for structs, whose implementations were, although repetitive, not intuitive especially for users unfamiliar with Haskell. In Copilot 4.2, it is now possible to define those methods automatically by relying on default method implementations that work well for most cases, although users retain the ability to customize those methods if desired.
We have increased test coverage in
copilot-core, reaching full coverage of the public interface.
The interface of copilot-core has also been simplified,
deprecating record fields of an existential type UExpr, which were
largely unused outside of Copilot’s internals.
The new implementation is compatible with versions of GHC from 8.6 to 9.10, as well as with Stackage Nightly.
This release has been made possible thanks to key submissions from Frank Dedden (@fdedden), Ryan Scott (@RyanGlScott), and Kyle Beechly (@kaBeech), the last of which is also a first-time contributor to the project. We are grateful to them for their timely contributions, especially during the holidays, and for making Copilot better every day. We also want to thank the attendees of Zurihac 2024 for technical discussions that helped find the right solutions to some of the problems addressed by this release.
Details are available here, and here.
As always, we’re releasing exactly 2 months since the last release. Our next release is scheduled for Mar 7th, 2025.
We want to remind the community that Copilot is now accepting code contributions from external participants again. Please see the discussions and the issues to learn how to participate.
Current emphasis is on improving the codebase in terms of performance, stability and test coverage, removing unnecessary dependencies, hiding internal definitions, formatting the code to meet our new coding standards, and simplifying the Copilot interface. Users are encouraged to participate by opening issues, asking questions, extending the implementation, and sending bug fixes via our github repo.
License
Copilot is distributed under the BSD-3-Clause license, which can be found here.
Acknowledgements
We are grateful for NASA Contract NNL08AD13T to Galois, Inc. and the National Institute of Aerospace, which partially supported this work.
Additionally NASA Langley contracts 80LARC17C0004 and NNL09AA00A supported further development of Copilot.
We would like to thank Kaveh Darafsheh (NASA Langley Research Center) for his help with testing Copilot. In addition numerous people have helped with smaller things, reporting bugs etc. Thanks to all of them!