This file documents what a Coq developer needs to know about the Dune-based build system. If you want to enhance the build system itself (or are curious about its implementation details), see build-system.dev.txt, and in particular its initial HISTORY section.

About Dune

Coq can now be built using Dune.

Quick Start

Usually, using the latest version of Dune is recommended, see the first line of the dune-project file for the minimum required version.

It is strongly recommended that you use the helper targets available in Makefile.dune, make -f Makefile.dune will display help. Note that dune will call configure for you if needed, so no need to call ./configure in the regular development workflow.

dune build @install will build all the public Coq artifacts; dune build will build all the targets in the workspace, including tests and documentations.

Dune will get confused if it finds leftovers of in-tree compilation, so please be sure your tree is clean from objects files generated by the make-based system.

Dune places build artifacts in a separate directory _build; it will also generate an .install file so files can be properly installed by package managers.

Contrary to other systems, Dune doesn't use a global Makefile but local build files named dune that are later composed to form a global build.

As a developer, Dune should take care of all OCaml-related build tasks including library management, merlin files, and linking order. You are are not supposed to modify the dune files unless you are adding a new binary, library, or plugin.

Per-User Custom Settings

Dune will read the file ~/.config/dune/config; see man dune-config. Among others, you can set in this file the custom number of build threads (jobs N) and display options (display _mode_).

Running binaries [coqtop / coqide]

Running coqtop directly with dune exec -- coqtop won't in general work well unless you are using dune exec -- coqtop -noinit. The coqtop binary doesn't depend itself on Coq's prelude, so plugins / vo files may go stale if you rebuild only coqtop.

Instead, you should use the provided "shims" for running coqtop and coqide in a fast build. In order to use them, do:

$ dune exec -- dev/shim/coqtop-prelude

or quickide / dev/shim/coqide-prelude for CoqIDE, etc.... See dev/shim/dune for a complete list of targets. These targets enjoy quick incremental compilation thanks to -opaque so they tend to be very fast while developing.

Note that for a fast developer build of ML files, the check target is faster, as it doesn't link the binaries and uses the non-optimizing compiler.

Targets

The default dune target is dune build (or dune build @install), which will scan all sources in the Coq tree and then build the whole project, creating an "install" overlay in _build/install/default.

You can build some other target by doing dune build $TARGET, where $TARGET can be a .cmxa, a binary, a file that Dune considers a target, an alias, etc...

In order to build a single package, you can do dune build $PACKAGE.install.

A very useful target is dune build @check, that will compile all the ml files in quick mode.

Dune also provides targets for documentation, testing, and release builds, please see below.

Documentation and testing targets

Coq's test-suite can be run with dune runtest; given that dune still invokes the test-suite makefile, the environment variable NJOBS will control the value of the -j option that is passed to make; common call NJOBS=8 dune runtest. This will be resolved in the future once the test suite is ported to Dune rules.

There is preliminary support to build the API documentation and reference manual in HTML format, use dune build {@doc,@refman-html} to generate them.

So far these targets will build the documentation artifacts, however no install rules are generated yet.

Developer shell

You can create a developer shell with dune utop $library, where $library can be any directory in the current workspace. For example, dune utop engine or dune utop plugins/ltac will launch utop with the right libraries already loaded.

Note that you must invoke the #rectypes;; toplevel flag in order to use Coq libraries. The provided .ocamlinit file does this automatically.

ocamldebug

You can use ocamldebug with Dune; after a build, do:

dune exec -- dev/dune-dbg coqc foo.v
(ocd) source dune_db

to start coqc.byte foo.v, other targets are {checker,coqide,coqtop}:

dune exec -- dev/dune-dbg checker foo.vo
(ocd) source dune_db

Unfortunately, dependency handling is not fully refined / automated, you may find the occasional hiccup due to libraries being renamed, etc... Please report any issue.

For running in emacs, use coqdev-ocamldebug from coqdev.el.

Note: If you are using OCaml >= 4.08 you need to use

(ocd) source dune_db_408

or

(ocd) source dune_db_409

depending on your OCaml version. This is due to several factors:

• OCaml >= 4.08 doesn't allow doubly-linking modules, however source is not re entrant and seems to doubly-load in the default setup, see https://github.com/coq/coq/issues/8952
• OCaml >= 4.09 comes with dynlink already linked in so we need to modify the list of modules loaded.

Dropping from coqtop:

The following commands should work:

dune exec -- dev/shim/coqbyte-prelude
> Drop.
# #directory "dev";;
# #use "include_dune";;

Compositionality, developer and release modes.

By default [in "developer mode"], Dune will compose all the packages present in the tree and perform a global build. That means that for example you could drop the ltac2 folder under plugins and get a build using ltac2, that will use the current Coq version.

This is very useful to develop plugins and Coq libraries as your plugin will correctly track dependencies and rebuild incrementally as needed.

However, it is not always desirable to go this way. For example, the current Coq source tree contains two packages [Coq and CoqIDE], and in the OPAM CoqIDE package we don't want to build CoqIDE against the local copy of Coq. For this purpose, Dune supports the -p option, so dune build -p coqide will build CoqIDE against the system-installed version of Coq libs, and use a "release" profile that for example enables stronger compiler optimizations.

OPAM file generation

.opam files are automatically generated by Dune from the package descriptions in the dune-project file; see Dune's manual for more details.

Stanzas

dune files contain the so-called "stanzas", that may declare:

• libraries,
• executables,
• documentation, arbitrary blobs.

The concrete options for each stanza can be seen in the Dune manual, but usually the default setup will work well with the current Coq sources. Note that declaring a library or an executable won't make it installed by default, for that, you need to provide a "public name".

Workspaces and Profiles

Dune provides support for tree workspaces so the developer can set global options --- such as flags --- on all packages, or build Coq with different OPAM switches simultaneously [for example to test compatibility]; for more information, please refer to the Dune manual.

Inlining reports

The ireport profile will produce standard OCaml inlining reports. These are to be found under _build/default/$lib/$lib.objs/$module.$round.inlining.org and are in Emacs org-mode format.

Note that due to https://github.com/ocaml/dune/issues/1401 , we must perform a full rebuild each time as otherwise Dune will remove the files. We hope to solve this in the future.

Planned and Advanced features

Dune supports or will support extra functionality that may result very useful to Coq, some examples are:

• Cross-compilation.
• Automatic Generation of OPAM files.
• Multi-directory libraries.

FAQ

• I get "Error: Dynlink error: Interface mismatch":

You are likely running a partial build which doesn't include implicitly loaded plugins / vo files. See the "Running binaries [coqtop / coqide]" section above as to how to correctly call Coq's binaries.

Dune cheat sheet

• dune build build all targets in the current workspace
• dune build @check build all ML targets as fast as possible, setup merlin
• dune utop $dir open a shell for libraries in $dir
• dune exec -- $file build and execute binary $file, can be in path or be an specific name
• dune build _build/$context/$foo build target $foo$ in $context, with build dir layout
• dune build _build/install/$context/foo build target $foo$ in $context, with install dir layout

packaging:

• dune subst generate metadata for a package to be installed / distributed, necessary for opam
• dune build -p $pkg build a package in release mode