dune/doc/quick-start.rst

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**********
Quickstart
**********
This document gives simple usage examples of Jbuilder. You can also look at
`examples <https://github.com/ocaml/dune/tree/master/example>`__ for
complete examples of projects using Jbuilder.
Building a hello world program
==============================
In a directory of your choice, write this ``jbuild`` file:
.. code:: scheme
(jbuild_version 1)
;; This declare the hello_world executable implemented by hello_world.ml
(executable
((name hello_world)))
This ``hello_world.ml`` file:
.. code:: ocaml
print_endline "Hello, world!"
And build it with:
.. code:: bash
jbuilder build hello_world.exe
The executable will be built as ``_build/default/hello_world.exe``. Note that
native code executables will have the ``.exe`` extension on all platforms
(including non-Windows systems).
Building a hello world program using Lwt
========================================
In a directory of your choice, write this ``jbuild`` file:
.. code:: scheme
(jbuild_version 1)
(executable
((name hello_world)
(libraries (lwt.unix))))
This ``hello_world.ml`` file:
.. code:: ocaml
Lwt_main.run (Lwt_io.printf "Hello, world!\n")
And build it with:
.. code:: bash
jbuilder build hello_world.exe
The executable will be built as ``_build/default/hello_world.exe``
Building a hello world program using Core and Jane Street PPXs
==============================================================
Write this jbuild:
.. code:: scheme
(jbuild_version 1)
(executable
((name hello_world)
(libraries (core))
(preprocess (pps (ppx_jane)))
))
This ``hello_world.ml`` file:
.. code:: ocaml
open Core
let () =
Sexp.to_string_hum [%sexp ([3;4;5] : int list)]
|> print_endline
And build it with:
.. code:: bash
jbuilder build hello_world.exe
The executable will be built as ``_build/default/hello_world.exe``
Defining a library using Lwt and ocaml-re
=========================================
Write this jbuild:
.. code:: scheme
(jbuild_version 1)
(library
((name mylib)
(public_name mylib)
(libraries (re lwt))))
The library will be composed of all the modules in the same directory.
Outside of the library, module ``Foo`` will be accessible as
``Mylib.Foo``, unless you write an explicit ``mylib.ml`` file.
You can then use this library in any other directory by adding ``mylib``
to the ``(libraries ...)`` field.
Setting the OCaml compilation flags globally
============================================
Write this jbuild at the root of your project:
.. code:: scheme
(env
(dev
(flags (:standard -w +42)))
(release
(flags (:standard -O3))))
`dev` and `release` correspond to build profiles. The build profile
can be selected from the command line with `--profile foo` or from a
`dune-workspace` file by writing:
.. code:: scheme
(profile foo)
Using cppo
==========
Add this field to your ``library`` or ``executable`` stanzas:
.. code:: scheme
(preprocess (action (run ${bin:cppo} -V OCAML:${ocaml_version} ${<})))
Additionally, if you are include a ``config.h`` file, you need to
declare the dependency to this file via:
.. code:: scheme
(preprocessor_deps (config.h))
Using the .cppo.ml style like the ocamlbuild plugin
---------------------------------------------------
Write this in your jbuild:
.. code:: scheme
(rule
((targets (foo.ml))
(deps (foo.cppo.ml <other files that foo.ml includes>))
(action (run ${bin:cppo} ${<} -o ${@}))))
Defining a library with C stubs
===============================
Assuming you have a file called ``mystubs.c``, that you need to pass
``-I/blah/include`` to compile it and ``-lblah`` at link time, write
this jbuild:
.. code:: scheme
(jbuild_version 1)
(library
((name mylib)
(public_name mylib)
(libraries (re lwt))
(c_names (mystubs))
(c_flags (-I/blah/include))
(c_library_flags (-lblah))))
Defining a library with C stubs using pkg-config
================================================
Same context as before, but using ``pkg-config`` to query the
compilation and link flags. Write this jbuild:
.. code:: scheme
(jbuild_version 1)
(library
((name mylib)
(public_name mylib)
(libraries (re lwt))
(c_names (mystubs))
(c_flags (:include c_flags.sexp))
(c_library_flags (:include c_library_flags.sexp))))
(rule
((targets (c_flags.sexp
c_library_flags.sexp))
(deps (config/discover.exe))
(action (run ${<} -ocamlc ${OCAMLC}))))
Then create a ``config`` subdirectory and write this ``jbuild``:
.. code:: scheme
(jbuild_version 1)
(executable
((name discover)
(libraries (base stdio configurator))))
as well as this ``discover.ml`` file:
.. code:: ocaml
open Base
open Stdio
module C = Configurator
let write_sexp fn sexp =
Out_channel.write_all fn ~data:(Sexp.to_string sexp)
let () =
C.main ~name:"mylib" (fun c ->
let default : C.Pkg_config.package_conf =
{ libs = ["-lblah"]
; cflags = []
}
in
let conf =
match C.Pkg_config.get c with
| None -> default
| Some pc ->
Option.value (C.Pkg_config.query pc ~package:"blah") ~default
in
write_sexp "c_flags.sexp" (sexp_of_list sexp_of_string conf.cflags);
write_sexp "c_library_flags.sexp" (sexp_of_list sexp_of_string conf.libs))
Using a custom code generator
=============================
To generate a file ``foo.ml`` using a program from another directory:
.. code:: scheme
(jbuild_version 1)
(rule
((targets (foo.ml))
(deps (../generator/gen.exe))
(action (run ${<} -o ${@}))))
Defining tests
==============
Write this in your ``jbuild`` file:
.. code:: scheme
(jbuild_version 1)
(alias
((name runtest)
(deps (my-test-program.exe))
(action (run ${<}))))
And run the tests with:
.. code:: bash
jbuilder runtest
Building a custom toplevel
==========================
A toplevel is simply an executable calling ``Topmain.main ()`` and
linked with the compiler libraries and ``-linkall``. Moreover,
currently toplevels can only be built in bytecode.
As a result, write this in your ``jbuild`` file:
.. code:: scheme
(jbuild_version 1)
(executable
((name mytoplevel)
(libraries (compiler-libs.toplevel mylib))
(link_flags (-linkall))
(modes (byte))))
And write this in ``mytoplevel.ml``
.. code:: ocaml
let () = Topmain.main ()