Xcode 5.1のリリースからこんな感じらしい
macでbundle installしたら以下のエラーが出た
... Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension. /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb checking for ruby/util.h... yes creating Makefile make "DESTDIR=" compiling bcrypt_ext.c compiling crypt.c compiling crypt_blowfish.c compiling crypt_gensalt.c compiling wrapper.c linking shared-object bcrypt_ext.bundle clang: error: unknown argument: '-multiply_definedsuppress' [-Wunused-command-line-argument-hard-error-in-future] clang: note: this will be a hard error (cannot be downgraded to a warning) in the future make: *** [bcrypt_ext.bundle] Error 1 Gem files will remain installed in /path/to/rails/vendor/bundle/ruby/2.0.0/gems/bcrypt-3.1.7 for inspection. Results logged to /path/to/rails/vendor/bundle/ruby/2.0.0/gems/bcrypt-3.1.7/ext/mri/gem_make.out An error occurred while installing bcrypt (3.1.7), and Bundler cannot continue. Make sure that `gem install bcrypt -v '3.1.7'` succeeds before bundling.
エラーをみたところによるとclang によるビルドエラーらしい
Xcode Release Notes
で、解決方法もここに書いてあるけど、ARCHFLAGSの環境変数を設定しつつ、bcryptをインストールしてみたらうまくいった
$ sudo ARCHFLAGS=-Wno-error=unused-command-line-argument-hard-error-in-future bundle install --path vendor/bundle
とかやって、再度bundle installしたらいけた