Iris Coq Development [coqdoc]

This is the Coq development of the Iris Project, which includes MoSeL, a general proof mode for carrying out separation logic proofs in Coq.

For using the Coq library, check out the API documentation.

For understanding the theory of Iris, a LaTeX version of the core logic definitions and some derived forms is available in tex/iris.tex. A compiled PDF version of this document is available online.

Side-effects

Importing Iris has some side effects as the library sets some global options.

• First of all, Iris imports std++, so the std++ side-effects apply.
• On top of that, Iris imports ssreflect, which replaces the default rewrite tactic with the ssreflect version. However, done is overwritten to keep using the std++ version of the tactic. We also set SsrOldRewriteGoalsOrder and re-open general_if_scope to un-do some effects of ssreflect.

Building Iris

Prerequisites

This version is known to compile with:

• Coq 8.19.2 / 8.20.0
• A development version of std++

Generally we always aim to support the last two stable Coq releases. Support for older versions will be dropped when it is convenient.

If you need to work with older versions of Coq, you can check out the tags for old Iris releases that still support them.

Working with Iris

To use Iris in your own proofs, we recommend you install Iris via opam (2.0.0 or newer). To obtain the latest stable release, you have to add the Coq opam repository:

opam repo add coq-released https://coq.inria.fr/opam/released

To obtain a development version, also add the Iris opam repository:

opam repo add iris-dev https://gitlab.mpi-sws.org/iris/opam.git

Either way, you can now install Iris:

• opam install coq-iris will install the libraries making up the Iris logic, but leave it up to you to instantiate the program_logic.language interface to define a programming language for Iris to reason about.
• opam install coq-iris-heap-lang will additionally install HeapLang, the default language used by various Iris projects.

To fetch updates later, run opam update && opam upgrade.

Be notified of breaking changes

We do not guarantee backwards-compatibility, so upgrading Iris may break your Iris-using developments. If you want to be notified of breaking changes, please let us know your account name on the MPI-SWS GitLab so we can add you to the notification group. Note that this excludes the "unstable" and "deprecated" packages (see below).

Use of Iris in submitted artifacts

If you are using Iris as part of an artifact submitted for publication with a paper, we recommend you make the artifact self-contained so that it can be built in the future without relying in any other server to still exist. However, if that is for some reason not possible, and if you are using opam to obtain the right version of Iris and you used a dev.* version, please let us know which exact Iris version you artifact relies on so that we can add it to this wiki page and avoid removing it from our opam repository in the future.

Working on Iris

See the contribution guide for information on how to work on the Iris development itself.

Directory Structure

Iris is structured into multiple packages, some of which contain multiple modules in separate folders.

• The iris package contains the language-independent parts of Iris.
  • The folder prelude contains modules imported everywhere in Iris.
  • The folder algebra contains the COFE and CMRA constructions as well as the solver for recursive domain equations.
    • The subfolder lib contains some general derived RA constructions.
  • The folder bi contains the BI++ laws, as well as derived connectives, laws and constructions that are applicable for general BIs.
    • The subfolder lib contains some general derived logical constructions.
  • The folder proofmode contains MoSeL, which extends Coq with contexts for intuitionistic and spatial BI++ assertions. It also contains tactics for interactive proofs. Documentation can be found in proof_mode.md.
  • The folder base_logic defines the Iris base logic and the primitive connectives. It also contains derived constructions that are entirely independent of the choice of resources.
    • The subfolder lib contains some generally useful derived constructions. Most importantly, it defines composable dynamic resources and ownership of them; the other constructions depend on this setup.
  • The folder program_logic specializes the base logic to build Iris, the program logic. This includes weakest preconditions that are defined for any language satisfying some generic axioms, and some derived constructions that work for any such language.
  • The folder si_logic defines a "plain" step-indexed logic and shows that it is an instance of the BI interface.
• The iris_heap_lang package defines the ML-like concurrent language HeapLang and provides tactic support and proof mode integration.
  • The subfolder lib contains a few derived constructions within this language, e.g., parallel composition. For more examples of using Iris and heap_lang, have a look at the Iris Examples.
• The iris_unstable package contains libraries that are not yet ready for inclusion in Iris proper. For each library, there is a corresponding "tracking issue" in the Iris issue tracker (also linked from the library itself) which tracks the work that still needs to be done before moving the library to Iris. No stability guarantees whatsoever are made for this package.
• The iris_deprecated package contains libraries that have been removed from Iris proper, but are kept around to give users some more time to switch to their intended replacements. The individual libraries come with comments explaining the deprecation and making recommendations for what to use instead. No stability guarantees whatsoever are made for this package.
• The folder tests contains modules we use to test our infrastructure. These modules are not installed by make install, and should not be imported.

Note that the unstable and deprecated packages are not released, so they only exist in the development version of Iris.

Case Studies

The following is a (probably incomplete) list of case studies that use Iris, and that should be compatible with this version:

• Iris Examples is where we collect miscellaneous case studies that do not have their own repository.
• LambdaRust is a Coq formalization of the core Rust type system.
• GPFSL is a logic for release-acquire and relaxed memory.
• Iron is a linear separation logic built on top of Iris for precise reasoning about resources (such as making sure there are no memory leaks).
• Actris is a separation logic built on top of Iris for session-type based reasoning of message-passing programs.

Further Resources

Getting along with Iris in Coq:

• The coding style is documented in the style guide.
• Iris proof patterns and conventions are documented in the proof guide.
• Various notions of equality and logical entailment in Iris and their Coq interface are described in the equality docs.
• The Iris tactics are described in the the Iris Proof Mode (IPM) / MoSeL documentation as well as the HeapLang documentation.
• The generated coqdoc is available online.

Contacting the developers:

• Discussion about the Iris Coq development happens on the mailing list [email protected] and in the Iris Chat. This is also the right place to ask questions.
• If you want to report a bug, please use the issue tracker, which requires an MPI-SWS GitLab account. The chat page describes how to create such an account.
• To contribute to Iris itself, see the contribution guide.

Miscellaneous:

• Information on how to set up your editor for unicode input and output is collected in editor.md.
• If you are writing a paper that uses Iris in one way or another, you could use the Iris LaTeX macros for typesetting the various Iris connectives.