This repository contains the current development state of a new verified extraction from Rocq to OCaml, based on MetaRocq.
Technically, the extraction targets Malfunction, which is a specification of Lambda, the internal language of the OCaml compiler.
We use Malfunction as target for extraction from Rocq, and rely on the Malfunction and OCaml compilers to obtain .cmx files that will behave like .cmx files created by Rocq's current extraction process and the Ocaml compiler.
In particular, Rocq programs extracted like this can interact with other OCaml programs and with Rocq programs extracted using the existing extraction.
The implementation of extraction is fully functional and supports all of Rocq's constructs including primitive integers, floats and arrays, but the cofixpoint to lazy/force translations is not verified yet. The article "Verified Extraction from Coq to OCaml" by Yannick Forster, Matthieu Sozean and Nicolas Tabareau, published and awarded at PLDI'24, describes this development.
See the online documentation for more information on the development.
opam switch create coq-malfunction --packages="ocaml-variants.4.14.1+options,ocaml-option-flambda"
eval $(opam env --switch=coq-malfunction)
opam repo add coq-released https://coq.inria.fr/opam/released
opam pin -n -y "https://github.com/MetaRocq/metarocq.git#v1.3.2-8.19"
opam pin -n -y "https://github.com/stedolan/malfunction.git#master"
opam install . --deps-only
make -j 4
After From VerifiedExtraction Require Import Extraction.
the commands Verified Extraction <definition> and Verified Extraction <definition> "<file>.mlf" can be used to run the new extraction process.
Multiple functions can be extracted at the same time with Verified Extraction (<d1>,<d2>,...).
To add an mli file one can add the output of the (unverified) generator MetaRocq Run Print mli <definition>. to a .mli file.
Note that this metaprogram does not (yet) take into account the reordering of
A0EF
constructors, besides the one for booleans (see Extract Inductives below).
It won't output declarations for unit, bool, list, option and prod that have matching representations in OCaml.
Verified Extraction supports the following options:
-time: prints compilation and run times-typed: uses typed extraction to perform more agressive argument removal-bypass-qeds: by default, Qed's proofs are turned into opaque constants during reification in MetaRocq, so that the reified environment is smaller, this bypasses this behavior and reifies everything (can be uterly slow). Axioms are turned into external function calls, so if some remain in the extracted code they will have to be implemented (in the producedAxioms.mlfile)-compile-plugin: compile the code as a Rocq plugin that can be loaded.-compile-with-coq: compile the code as a standalone program that however links with Rocq's codebase (c.f. theRocqMsgFFi.vfile)-compile: compile the code as a fully standalone program not depending on Rocq (can be run from the shell)-optimize: Use "malfunction -O2" to compile produced code.-load: load the plugin into Rocq-run: Runs the compiled program or linked plugin and readback it's computed value. Plugins using theRocqMsgFFI.vcan output information in Rocq's info, notice and error channels while running.-verbose: More verbose compiler output-fmt: Use malfunctions automatic formatting to produce the .mlf file (for more readable generated code)-unsafe: Use unsafe optimizations (all of them, or a subset by listing some of the following flags separated by spaces):cofix-to-lazy: unverified cofixpoints to lazy/force translationinlining: honorVerified Extract Inlinedirectives.unboxing: perform unboxing of types having a single constructor with a single computational argument This is run after typed erasure for more opportunities to unbox.betared: perform apparent beta reductions (useful when combined with inlining)
Verified Extraction also supports the directives:
Verified Extract Inductives [ ind [ name [ tags ] ], .. ]: this declares a reordering of constructors to match existing ocaml datatype representations (tags are natural numbers). This reordering phase is verified. By default, Rocq's booleansInductive bool := true | falseare mapped to OCaml'stype bool = false | trueby swapping their constructor tags.Verified Extract Inline cst: declarescstto be inlined (expanded everywhere) during extraction. This phase is NOT verified at the moment.
- the
theoriesdirectory contains the Rocq files with implementation and verification of the pluginMalfunction.vcontains the syntax definition of Malfunction. It is a direct, line-to-line port of the OCaml filemalfunction.mlto Rocq.SemanticsSpec.vdefines an inductive big-step evaluation predicate.Compile.vdefines a compilation function of lambda box to Malfunction.CompileCorrect.vproves the correctness of this function, using the correctness proof of case analysis inMcase.vInterpreter.vcontains an interpretation function, which is close tomalfunction_interpreter.ml, and a proof that values according to the evaluation predicate are also found by the interpreter. Note that since the interpreter is not necessarily terminating we switch of Rocq's termination checker, meaning this proof can only be seen as a sanity check.Serialize.vcontains seralization functions into s-expressions. There is also a parser inDeserialize.v, used for testing.Pipeline.vcomposes the full extraction pipeline from Rocq to MalfunctionPipelineCorrect.vcomposes the correctness proof of the extraction pipelineFirstorder.vderives interoperability results for first-order functions
- the
plugindirectory contains the code of the extraction plugin extracted using Rocq's OCaml extraction viatheories/Extraction.v. This is packaged into an intermediate extraction plugin. - the
plugin/plugin-bootstrapdirectory contains the code of the extraction plugin extracted using the intermediate extraction plugin. This is packaged into the final verified extraction plugin. - the
examplesdirectory contains various examples how to use the new verified extraction plugin. - the
benchmarksdirectory allows re-producing benchmarks from the paper.
The project is developed by Yannick Forster, Matthieu Sozeau, Pierre-Marie Pédrot, and Nicolas Tabareau.
Copyright (c) 2022--2025 Yannick Forster, Matthieu Sozeau, Nicolas Tabareau