“extconf.rb failed” message while installing Rails

Question

Newbie here. I've searched for other similar questions on the site but still wasn't able to solve the problem. I've installed Ruby 2.0.0 and RubyGem 2.0.3, but when I'm trying to install Rails 4.0.0 I got:

    Building native extensions.  This could take a while...
ERROR:  Error installing rails:
    ERROR: Failed to build gem native extension.
    /Users/yuanhunglo/.rvm/rubies/ruby-2.0.0-p0/bin/ruby extconf.rb
*** extconf.rb failed ***
Could not create Makefile due to some reason, probably lack of necessary
libraries and/or headers.  Check the mkmf.log file for more details.  You may
need configuration options.

Provided configuration options:
    --with-opt-dir
    --with-opt-include
    --without-opt-include=${opt-dir}/include
    --with-opt-lib
    --without-opt-lib=${opt-dir}/lib
    --with-make-prog
    --without-make-prog
    --srcdir=.
    --curdir
    --ruby=/Users/yuanhunglo/.rvm/rubies/ruby-2.0.0-p0/bin/ruby
    --with-atomic_reference-dir
    --without-atomic_reference-dir
    --with-atomic_reference-include
    --without-atomic_reference-include=${atomic_reference-dir}/include
    --with-atomic_reference-lib
    --without-atomic_reference-lib=${atomic_reference-dir}/
/Users/yuanhunglo/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/mkmf.rb:431:in `try_do': The compiler failed to generate an executable file. (RuntimeError)
You have to install development tools first.
    from /Users/yuanhunglo/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/mkmf.rb:516:in `try_link0'
    from /Users/yuanhunglo/.rvm/rubies/ruby-2.0.0-p0/lib/ruby/2.0.0/mkmf.rb:814:in `try_run'
    from extconf.rb:22:in `<main>'


Gem files will remain installed in /Users/yuanhunglo/.rvm/gems/ruby-2.0.0-p0/gems/atomic-1.1.10 for inspection.
Results logged to /Users/yuanhunglo/.rvm/gems/ruby-2.0.0-p0/gems/atomic-1.1.10/ext/gem_make.out

I tried to install Rails by

gem install rails --version 4.0.0

I'm not sure if there's something wrong with the set up or if I still need to install something. Thanks in advance for your help.

Answer 1

It seems you're using OSX.

This error happens when you can't compile some extensions, in this case due to the lack of a compiler ("You have to install development tools first"). Open App Store, download XCode and, after installing it, click on "XCode" on the menu, go to Preferences -> Downloads -> Components and download "Command Line Tools".