Swift system module for libruby

What's New



Add Xcode config-file generation - now generates CRuby.xcconfig.

Remove -fdeclspec references -- fixed in modern clang.

Platforms License


Wrap libruby for SwiftPM or Xcode. Easily reconfigure for your Ruby installation.

See RubyGateway for a high-level Swift-Ruby integration framework.

Tested with environments:

  • macOS 14 system Ruby (still 2.6 - beware)
  • macOS Homebrew, RBEnv, RVM
  • macOS bespoke installation
  • Ubuntu Jammy bespoke, RBEnv, RVM

And Ruby versions:

  • 2.6 - 3.3


CRuby comes set up to use the macOS system Ruby, and Xcode to provide C headers.

If you want to use a different Ruby then use the cfg-cruby script to rewrite the build config files.

For options other than macOS system Ruby, cfg-cruby generates a custom pkg-config file called CRuby.pc for swift build, and an Xcconfig file called CRuby.xcconfig for Xcode.

Swift Package Manager

Include this repo as a dependency in your project:

.package(url: "", majorVersion: 2)

To use a Ruby other than macOS system default you need to reconfigure. For example to set up Ruby 3.3.0 managed by rbenv:

swift package edit CRuby
./Packages/CRuby/cfg-cruby --mode rbenv --name 3.3.0
export PKG_CONFIG_PATH=$(pwd)/Packages/CRuby:$PKG_CONFIG_PATH
swift build

Either leave the CRuby package in edit mode or fork the repo, use that fork as your remote, and push your customizations back there.


Include this repo in your project. A git submodule works well. So either way you have a directory called CRuby. Then go to Build Settings for the Target where you want to do import CRuby and find Import Paths under Swift Compiler - Search Paths. Add the path to your CRuby directory - you can use ${SRCROOT} to substitute for the directory containing the project file.

Check Xcode is happy with an import CRuby line. This is using the macOS system default Ruby, probably a very old 2.6.

If you want to use a different Ruby, run cfg-cruby. This creates a file called CRuby.xcconfig that you need to include in the appropriate targets. Start here for help with using xcconfig files.

That's it: Xcode should now resolve CRuby against your chosen version.

Supported Ruby Configs

macOS system

Use the xcode-selected Xcode:

cfg-cruby --mode xcode

This configuration does not require a pkg-config file.

macOS Homebrew or Linux -dev package

cfg-cruby --mode pkgconfig --name <pkg-name>

Use pkg-config --list-all to see what you have installed.

The pkg-config setup is not directly consumable by SwiftPM. cfg-cruby uses it to create the CRuby.pc that is compatible with SwiftPM.

RBEnv or RVM

cfg-cruby --mode rbenv --name <version>


cfg-cruby --mode rvm --name <ruby name>

Something else

If you've built Ruby yourself or are using a different version manager that preserves the regular layout then:

cfg-cruby --path <full path to Ruby directory>

The path required is one to a directory that is called ruby-*something* and contains subdirectories including lib, include, and bin.


Welcome - github /


Distributed under the MIT license.


  • Swift Tools 5.4.0
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Last updated: Wed May 01 2024 14:44:44 GMT-0900 (Hawaii-Aleutian Daylight Time)