rake-compiler aims to help Gem developers while dealing with Ruby C extensions, simplifiying the code and reducing the duplication.

It follows *convention over configuration* and set an standarized structure to build and package C extensions in your gems.

This is the result of expriences dealing with several Gems that required native extensions across platforms and different user configurations where details like portability and clarity of code were lacking.

Let’s summarize what rake-compiler provides:

• No custom rake tasks required. Less code duplication and errors.

• Painlessly build extensions on different platforms (Linux, OSX and Windows).

• Allow multiple extensions be compiled inside the same gem.

• Mimics RubyGems installation process, so helps as test environment.

• Simplify cross platform compilation of extensions (target Windows from Linux).

Usage of rake-compiler is pretty much straight forward.

First, you need to install the gem:

$ gem install rake-compiler

Since this package is in constant evolution, you could try installing it from GitHub:

$ gem install luislavena-rake-compiler --source http://gems.github.com

The development gem is usually in pretty good shape actually.

Now that you have the gem installed, let’s give your project some structure.

Let’s say we want to compile an extension called ‘hello_world’, so we should organize the code and folders that will help rake-compiler do it’s job:

|-- ext
|   `-- hello_world
|       |-- extconf.rb
|       `-- hello_world.c
|-- lib
`-- Rakefile

TIP: Having a consistent folder structure will help developers and newcomers to find code and also contribute back to your project more easily.

So now it’s time to introduce the code to compile our extension:

# File: Rakefile
require 'rake/extensiontask'
Rake::ExtensionTask.new('hello_world')

Ok, that’s it. No other line of code.

Those two lines of code automatically added the needed rake tasks to build the hello_world extension:

$ rake -T
(in /home/user/my_extesion)
rake compile                # Compile the extension(s)
rake compile:hello_world    # Compile just the hello_world extension

Simply calling compile:

$ rake compile

Will do all the compile process for us, putting the result extension inside lib directory.

NOTE: Please be aware that building C extensions requires the proper development environment for your Platform, which includes libraries, headers and build tools. Check your distro / vendor documentation on how to install it.

A common usage scenario of rake-compiler is generate native gems that bundles your extensions.

This got over-simplified with Rake::ExtensionTask:

# somewhere in your Rakefile, define your gem spec
spec = Gem::Specification.new do |s|
  s.name = "my_gem"
  s.platform = Gem::Platform::RUBY
  s.extensions = FileList["ext/**/extconf.rb"]
end
# add your default gem packing task
Rake::GemPackageTask.new(spec) do |pkg|
end
# feed your ExtensionTask with your spec
Rake::ExtensionTask.new('hello_world', spec)

Now, as usual, you can build your pure-ruby gem (standard output):

$ rake gem
(in /projects/oss/my_gem.git)
mkdir -p pkg
  Successfully built RubyGem
  Name: my_gem
  Version: 0.1.0
  File: my_gem-0.1.0.gem
mv my_gem-0.1.0.gem pkg/my_gem-0.1.0.gem

Plus, you have the functionality to build native versions of the gem:

# rake native gem
(... compilation output ...)
mkdir -p pkg
  Successfully built RubyGem
  Name: my_gem
  Version: 0.1.0
  File: my_gem-0.1.0.gem
mv my_gem-0.1.0.gem pkg/my_gem-0.1.0.gem
  Successfully built RubyGem
  Name: my_gem
  Version: 0.1.0
  File: my_gem-0.1.0-x86-mingw32.gem
mv my_gem-0.1.0-x86-mingw32.gem pkg/my_gem-0.1.0-x86-mingw32.gem

You get two gems for the price of one.

In case you want to bend the convention established, rake-compiler let you personalize several settings for Rake::ExtensionTask:

Rake::ExtensionTask.new do |ext|
  ext.name = 'hello_world'                # indicate the name of the extension.
  ext.ext_dir = 'ext/weird_world'         # search for 'hello_world' inside it.
  ext.lib_dir = 'lib/my_lib'              # put binaries into this folder.
  ext.config_script = 'custom_extconf.rb' # use instead of 'extconf.rb' default
  ext.tmp_dir = 'tmp'                     # temporary folder used during compilation.
  ext.source_pattern = "*.{c,cpp}"        # monitor file changes to allow simple rebuild.
  ext.config_options << '--with-foo'      # supply additional configure options to config script.
  ext.gem_spec = spec                     # optional indicate which gem specification
                                          # will be used to based on.
end

rake-compiler provides now an standarized way to generate, from Linux or OSX both extensions and gem binaries for Windows!

It takes advantages from GCC host/target to build binaries (for target) on different OS (hosts).

Besides having the development tool chain installed (GCC), you should install also mingw32 cross compilation package.

Dependending on your operating system distribution, a simple apt-get install mingw32 will be enough.

Please check OSX documentation about installing mingw32 from macports.

You need to build Ruby for Windows.

Relax, no need to freak out. rake-compiler do it for you:

rake-compiler cross-ruby

And you’re done. It will automatically download, configure and compile latest stable version of Ruby for Windows, and place it into ~/.rake-compiler

If, instead, you want to build another version than the default one, please supply a VERSION:

rake-compiler cross-ruby VERSION=1.8.6-p114

Now, you only need to use additional options in your extension defintion:

Rake::ExtensionTask.new('my_extension', gem_spec) do |ext|
  ext.cross_compile = true                # enable cross compilation (requires cross compile toolchain)
  ext.cross_platform = 'i386-mswin32'     # forces the Windows platform instead of the default one
                                          # configure options only for cross compile
  ext.cross_config_options << '--with-something'
end

By default, cross compilation targets ‘i386-mingw32’ which is default GCC platform for Ruby.

To target gems for current Ruby official distribution, please force the platform to the one shown before.

Compiles keeps being simple:

rake cross compile

And now, build your gems for Windows is just 5 more letters:

rake cross native gem

And you’re done, yeah.

You can specify against with version of Ruby you want to build the extension:

rake cross compile RUBY_CC_VERSION=1.8

If you installed 1.9.1, you can do:

rake cross compile RUBY_CC_VERSION=1.9

rake-compiler is a work in progress and we will appreciate feedback during the development of it! (and contributions too!)

You can find more information about rake-compiler:

Blog: blog.mmediasys.com RubyForge: rubyforge.org/projects/rake-compiler GitHub: github.com/luislavena/rake-compiler

• Rake::JavaJarTask to generate jar packages and gems for JRuby.

  $ rake java gem

If you have any trouble, don’t hesitate to contact the author. As always, I’m not going to say “Use at your own risk” because I don’t want this library to be risky.

If you trip on something, I’ll share the liability by repairing things as quickly as I can. Your responsibility is to report the inadequacies.