Rscons

Software construction library inspired by SCons and implemented in Ruby

Installation

Add this line to your application's Gemfile:

gem "rscons"

And then execute:

$ bundle

Or install it yourself as:

$ gem install rscons

Usage

Rscons is a Ruby library. It can be called from a standalone Ruby script or it can be used with rake and called from your Rakefile.

Example: Building a C Program

Rscons::Environment.new do |env|
  env["CFLAGS"] << "-Wall"
  env.Program("program", Dir["**/*.c"])
end

Example: Building a D Program

Rscons::Environment.new do |env|
  env["DFLAGS"] << "-Wall"
  env.Program("program", Dir["**/*.d"])
end

Example: Cloning an Environment

main_env = Rscons::Environment.new do |env|
  # Store object files from sources under "src" in "build/main"
  env.build_dir("src", "build/main")
  env["CFLAGS"] = ["-DSOME_DEFINE", "-O3"]
  env["LIBS"] = ["SDL"]
  env.Program("program", Dir["src/**/*.cc"])
end

debug_env = main_env.clone do |env|
  # Store object files from sources under "src" in "build/debug"
  env.build_dir("src", "build/debug")
  env["CFLAGS"] -= ["-O3"]
  env["CFLAGS"] += ["-g", "-O0"]
  env.Program("program-debug", Dir["src/**/*.cc"])
end

Example: Custom Builder

class GenerateFoo < Rscons::Builder
  def run(target, sources, cache, env, vars)
    cache.mkdir_p(File.dirname(target))
    File.open(target, "w") do |fh|
      fh.puts <<EOF
#define GENERATED 42
EOF
    end
  end
end

Rscons::Environment.new do |env|
  env.GenerateFoo("foo.h", [])
  env.Program("a.out", Dir["*.c"])
end

Example: Custom Builder That Only Regenerates When Necessary

class CmdBuilder < Rscons::Builder
  def run(target, sources, cache, env, vars)
    cmd = ["cmd", "-i", sources.first, "-o", target]
    unless cache.up_to_date?(target, cmd, sources, env)
      cache.mkdir_p(File.dirname(target))
      system(cmd)
      cache.register_build(target, cmd, sources, env)
    end
  end
end

Rscons::Environment.new do |env|
  env.CmdBuilder("foo.gen", "foo_gen.cfg")
end

Example: Custom Builder Using Builder#standard_build()

class CmdBuilder < Rscons::Builder
  def run(target, sources, cache, env, vars)
    cmd = ["cmd", "-i", sources.first, "-o", target]
    standard_build("CmdBld #{target}", target, cmd, sources, env, cache)
  end
end

Rscons::Environment.new do |env|
  env.CmdBuilder("foo.gen", "foo_gen.cfg")
end

Example: Using different compilation flags for some sources

Rscons::Environment.new do |env|
  env["CFLAGS"] = ["-O3", "-Wall", "-DDEFINE"]
  env.add_build_hook do |build_op|
    if build_op[:target] =~ %r{build/third-party}
      build_op[:vars]["CFLAGS"] -= ["-Wall"]
    end
  end
  env.build_dir("src", "build")
  env.Program("program", Dir["**/*.cc"])
end

Each build hook block will be invoked for every build operation, so the block should test the target or sources if its action should only apply to some subset of build targets or source files.

The build_op parameter to the build hook block is a Hash describing the build operation with the following keys:

• :builder - Builder instance in use
• :target - String name of the target file
• :sources - Array of the source files
• :vars - Rscons::VarSet containing the construction variables to use The build hook can overwrite entries in build_op[:vars] to alter the construction variables in use for this specific build operation.

Example: Creating a static library

Rscons::Environment.new do |env|
  env.Library("mylib.a", Dir["src/**/*.c"])
end

Details

Default Builders

Rscons ships with a number of default builders:

• Library, which collects object files into a static library archive file
• Object, which compiles source files to produce an object file
• Program, which links object files to produce an executable

If you want to create an Environment that does not contain any builders, you can use the exclude_builders key to the Environment constructor.

Managing Environments

An Rscons::Environment consists of:

• a collection of construction variables
• a collection of builders
• a mapping of build directories from source directories
• a default build root to apply if no build directories are matched
• a collection of targets to build
• a collection of build hooks

When cloning an environment, the construction variables and builders are cloned, but the new environment does not inherit any of the targets, build hooks, build directories, or the build root from the source environment.

Cloned environments contain "deep copies" of construction variables. For example, in:

base_env = Rscons::Environment.new
base_env["CPPPATH"] = ["one", "two"]
cloned_env = base_env.clone
cloned_env["CPPPATH"] << "three"

base_env["CPPPATH"] will not include "three".

Construction Variable Naming

• uppercase strings - the default construction variables that Rscons uses
• lowercase symbols - Rscons options
• lowercase strings - reserved as user-defined construction variables

Contributing

1. Fork it
2. Create your feature branch (git checkout -b my-new-feature)
3. Commit your changes (git commit -am 'Add some feature')
4. Push to the branch (git push origin my-new-feature)
5. Create new Pull Request