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Bundlex is a multi-platform tool for compiling C and C++ code along with elixir projects, for use in NIFs, CNodes and Ports. The tool also provides a convenient way of accessing compiled code in elixir modules.

Bundlex has been tested on Linux, Mac OS and FreeBSD. There's some support for Windows as well, but it's experimental and unstable (see issues for details).

Bundlex also supports cross-compilation and has been tested with platforms running Nerves.

This tool is maintained by the Membrane Framework team.

Installation

To install, you need to configure Mix project as follows:

defmodule MyApp.Mixfile do
  use Mix.Project

  def project do
    [
      app: :my_app,
      compilers: [:bundlex] ++ Mix.compilers, # add bundlex to compilers
      deps: deps(),
      # ...
   ]
  end

  defp deps() do
    [
      {:bundlex, "~> 1.5"}
    ]
  end
end

and create bundlex.exs file in the project root folder, containing Bundlex project module:

defmodule MyApp.BundlexProject do
  use Bundlex.Project

  def project() do
    []
  end
end

Now your project does not contain any C sources, but should compile successfully, and some Bundlex messages should be printed while compilation proceeds.

Usage

Adding natives to project

Adding natives can be done in project/0 function of Bundlex project module in the following way:

defmodule MyApp.BundlexProject do
  use Bundlex.Project

  def project() do
    [
      natives: natives(Bundlex.platform),
      libs: libs()
    ]
  end

  defp natives(:linux) do
    [
      my_native: [
        sources: ["something.c", "linux_specific.c"],
        interface: :nif
      ],
      my_other_native: [
        sources: ["something_other.c", "linux_specific.c"],
        interface: :cnode
      ],
      my_other_native: [
        sources: ["something_more_other.c", "linux_specific.c"],
        interface: :port
      ]
    ]
  end

  defp natives(_platform) do
    [
      my_native: [
        sources: ["something.c", "multiplatform.c"],
        interface: :nif
      ],
      my_other_native: [
        sources: ["something_other.c", "multiplatform.c"],
        interface: :cnode
      ],
      my_other_native: [
        sources: ["something_more_other.c", "multiplatform.c"],
        interface: :port
      ]
    ]
  end

  defp libs() do
    [
      my_lib: [
        sources: ["something.c"],
        interface: :nif
      ],
      my_lib: [
        sources: ["something_other.c"],
        interface: :cnode
      ]
    ]
  end
end

As we can see, we can specify two types of resources:

  • natives - code implemented in C that will be used within Elixir code
  • libs - can be used by natives or other libs as dependencies

By default, the sources should reside in project_root/c_src/my_app directory.

For more details and available options, see Bundlex.Project.native_config.

Dependencies

Each native can have dependencies - libs that are statically linked to it and can be included in its native code like #include lib_name/some_header.h. The following rules apply:

  • To add dependencies from a separate project, it must be available via Mix.
  • Only libs can be added as dependencies.
  • Each dependency of a native must specify the same or no interface. If there exist multiple versions of dependency with different interfaces, the proper version is selected automatically.
  • A lib that specifies no interface can depend on libs with no interfaces only.

Compilation options

The following command-line arguments can be passed:

  • --store-scripts - if set, shell scripts are stored in the project root folder for further analysis.

Loading NIFs in modules

NIFs compiled with Bundlex can be loaded the same way as any other NIFs (see :erlang.load_nif/2), but Bundlex provides Bundlex.Loader module to save you some boilerplate:

defmodule MyApp.SomeNativeStuff do
  use Bundlex.Loader, nif: :my_nif

  def normal_function(a, b, c, d) do
    private_native_function(a+b, c+d)
  end

  defnif native_function(a, b)

  defnifp private_native_function(x, y)

end

Note that unlike when using :erlang.load_nif/2, here defs and defps can be used to create usual functions, native ones are declared with defnif and defnifp. This is achieved by creating a new module under the hood, and that is why the module passed to C macro ERL_NIF_INIT has to be succeeded by .Nif, i.e.

ERL_NIF_INIT(MyApp.SomeNativeStuff.Nif, funs, load, NULL, upgrade, unload)

Despite this, any native erlang macros and functions shall be used as usual, as described at http://erlang.org/doc/man/erl_nif.html

Interacting with CNodes

As in the case of NIFs, CNodes compiled with Bundlex can be used like any other CNodes (see built-in Node module), while some useful stuff for interacting with them is provided. Bundlex.CNode module contains utilities that make it easier to spawn and control CNodes, and allow them to treat them more like usual Elixir processes. Check out the documentation for more details.

Interacting with Ports

Similarly to CNodes Bundlex provides Bundlex.Port module for a little easier interacting with Ports. Please refer to the module's documentation to see how to use it.

Cross-compilation

With proper setup, Bundlex can support cross-compilation. When using Nerves it should work out of the box.

Not relying on Nerves and using your own toolchain is also possible, although it wasn't tested. In this scenario, the following environment variables need to be set during compilation (when changing the target bundlex also needs to be recompiled):

  • CROSSCOMPILE - value is not important, just needs to be set
  • CC - path to the C compiler for cross-compiling to the target
  • CFLAGS - C compilation flags
  • CXX - path to the C++ compiler for cross-compiling to the target
  • CXXFLAGS - C++ compilation flags
  • LDFLAGS - Linker flags

If you wish for Bundlex.get_target/0 to return accurate information about your target, set the following environment variables:

  • TARGET_ARCH - The target CPU architecture (e.g., arm, aarch64, mipsel, x86_64, riscv64)
  • TARGET_VENDOR - Vendor of your target platform
  • TARGET_OS - The targes OS (e.g. linux)
  • TARGET_ABI - The target ABI (e.g., gnueabihf, musl)

When cross-compiling some warnings may be raised about not being able to load nifs, but that's expected, since they are most likely built for different architecture.

Documentation of the native code

Bundlex provides a way to generate documentation of the native code. The documentation is generated using Doxygen.

To do so, run $ mix bundlex.doxygen command. The documentation is generated for each native separately. The documentation of the native project_name will be generated in doc/bundlex/project_name directory. Additionally, hex doc page with the link to the Doxygen documentation is generated in the pages/doxygen/project_name.md and should be included in the mix.exs file: 

defp docs do
  [
    extras: [
      "pages/doxygen/project_name.md",
      ...
    ],
    ...
  ]
end

If you want to keep own changes in the pages/doxygen/project_name.md file, you can use --no option to skip the generation of this file. Otherwise, if you want the file to be always overwritten, use --yes option.

After that, the documentation can be generated with mix docs command.

Include native documentation in the hex docs

To include the native documentation in the hex docs, you need to generate the documentation with $ mix bundlex.doxygen command and include hex page in the extras, before running $ mix hex.publish command.

More examples

More advanced examples can be found in our test_projects or in our repositories where we use Bundlex e.g. in Unifex.

Copyright 2018, Software Mansion

Software Mansion

Licensed under the Apache License, Version 2.0