Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension on Mac

Question

Built a new rails project using rails new blog and got a error message: Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

   exist  
   identical  README.rdoc
   identical  Rakefile
   identical  config.ru
   identical  .gitignore
   identical  Gemfile
       exist  app
   identical  app/assets/javascripts/application.js
   identical  app/assets/stylesheets/application.css
   identical  app/controllers/application_controller.rb
   identical  app/helpers/application_helper.rb
   identical  app/views/layouts/application.html.erb
   identical  app/assets/images/.keep
   identical  app/mailers/.keep
   identical  app/models/.keep
   identical  app/controllers/concerns/.keep
   identical  app/models/concerns/.keep
       exist  bin
   identical  bin/bundle
   identical  bin/rails
   identical  bin/rake
       exist  config
   identical  config/routes.rb
   identical  config/application.rb
   identical  config/environment.rb
       exist  config/environments
   identical  config/environments/development.rb
   identical  config/environments/production.rb
   identical  config/environments/test.rb
       exist  config/initializers
   identical  config/initializers/backtrace_silencers.rb
   identical  config/initializers/filter_parameter_logging.rb
   identical  config/initializers/inflections.rb
   identical  config/initializers/mime_types.rb
    conflict  config/initializers/secret_token.rb
Overwrite /Users/jianqiuhuang/Desktop/ruby/blog/config/initializers/secret_token.rb? (enter "h" for help) [Ynaqdh] y
       force  config/initializers/secret_token.rb
   identical  config/initializers/session_store.rb
   identical  config/initializers/wrap_parameters.rb
       exist  config/locales
   identical  config/locales/en.yml
   identical  config/boot.rb
   identical  config/database.yml
       exist  db
   identical  db/seeds.rb
       exist  lib
       exist  lib/tasks
   identical  lib/tasks/.keep
       exist  lib/assets
   identical  lib/assets/.keep
       exist  log
   identical  log/.keep
       exist  public
   identical  public/404.html
   identical  public/422.html
   identical  public/500.html
   identical  public/favicon.ico
   identical  public/robots.txt
       exist  test/fixtures
   identical  test/fixtures/.keep
       exist  test/controllers
   identical  test/controllers/.keep
       exist  test/mailers
   identical  test/mailers/.keep
       exist  test/models
   identical  test/models/.keep
       exist  test/helpers
   identical  test/helpers/.keep
       exist  test/integration
   identical  test/integration/.keep
   identical  test/test_helper.rb
       exist  tmp/cache
       exist  tmp/cache/assets
       exist  vendor/assets/javascripts
   identical  vendor/assets/javascripts/.keep
       exist  vendor/assets/stylesheets
   identical  vendor/assets/stylesheets/.keep
         run  bundle install
Fetching gem metadata from https://rubygems.org/..........
Fetching version metadata from https://rubygems.org/..
Resolving dependencies...
Using rake 10.4.2
Using i18n 0.7.0
Using minitest 4.7.5
Using multi_json 1.11.0
Using thread_safe 0.3.5
Using tzinfo 0.3.43
Using activesupport 4.0.0
Using builder 3.1.4
Using erubis 2.7.0
Using rack 1.5.2
Using rack-test 0.6.3
Using actionpack 4.0.0
Using mime-types 1.25.1
Using polyglot 0.3.5
Using treetop 1.4.15
Using mail 2.5.4
Using actionmailer 4.0.0
Using activemodel 4.0.0
Using activerecord-deprecated_finders 1.0.4
Using arel 4.0.2
Using activerecord 4.0.0
Using bundler 1.9.4
Using coffee-script-source 1.9.1.1
Using execjs 2.5.2
Using coffee-script 2.4.1
Using thor 0.19.1
Using railties 4.0.0
Using coffee-rails 4.0.1
Using hike 1.2.3
Using jbuilder 1.5.3
Using jquery-rails 3.1.2

Gem::Installer::ExtensionBuildError: ERROR: Failed to build gem native extension.

    /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/bin/ruby extconf.rb
mkmf.rb can't find header files for ruby at /System/Library/Frameworks/Ruby.framework/Versions/2.0/usr/lib/ruby/include/ruby.h


Gem files will remain installed in /var/folders/b0/spcr203s5vgb3f4sd8kfllhc0000gn/T/bundler20150422-979-i48mud/json-1.8.2/gems/json-1.8.2 for inspection.
Results logged to /var/folders/b0/spcr203s5vgb3f4sd8kfllhc0000gn/T/bundler20150422-979-i48mud/json-1.8.2/gems/json-1.8.2/ext/json/ext/generator/gem_make.out
An error occurred while installing json (1.8.2), and Bundler cannot continue.
Make sure that `gem install json -v '1.8.2'` succeeds before bundling.

Does anyone know what the problem is?

Answer 1

There are two things you can try:

1. Update bundler. Some versions of bundler, eg 1.5.0, might raise the above error that you ran into. Try this gem install bundler -v '= 1.5.1' or a version higher than 1.5.1
2. Try reinstalling ruby through rvm reinstall <version>

Answer 2

It seems that you are trying to create a new rails app on a folder that already exists and you shouldn't do it. First delete the previous installation, the "blog" folder, or choose another app name.

Answer 3

The problem was that I installed the newest version of Xcode and never open Xcode to complete the installation. Easy fix:

• Update Xcode
• Launch Xcode to complete installation

Then, you can do rails new <directory>