This section describes how to build and install binary programs with Dune.

Definig executables


Embedding build information into executables

Dune allows to embed build information such as versions in executbles via the special dune.build-info library. This library exposes a few informations about how the executable was built such as the version of the project containing the executable or the list of statically linked libraries with their versions. Printing the version at which the current executable was built is as simple as:

Printf.printf "version: %s\n"
  (match Build_info.V1.version with
   | None -> "n/a"
   | Some v -> Build_info.V1.Version.to_string v)

For libraries and executables from development repositories that don’t have version informations written directly in the dune-project file, the version is obtained by querying the version control system. For instance, the following git command is used in git repositories:

git describe --always --dirty

which produces a human readable version string of the form <version>-<commits-since-version>-<hash>[-dirty].

Note that in the case where the version string is ontained from the the version control system, the version string will only be written in the binary once it is installed or promoted to the source tree. In particular, if you evalute this expression as part of the build of your package, it will return None. This is to ensure that committing does not hurt your development experience. Indeed, if dune stored the version directly inside the freshly built binaries, then everytime you commit your code the version would change and dune would need to rebuild all the binaries and everything that depend on them, such as tests. Instead Dune leaves a placeholder inside the binary and fills it during installation or promotion.