Gem Install Debugger Error

Question

I am running Rails v4.0.2 on Mac OS 10.9.2 and I had everything smoothly. All of a sudden I'm getting an error saying gems are missing when I try rails server. I run bundle install and this is the output:

Fetching gem metadata from https://rubygems.org/.......
Fetching additional metadata from https://rubygems.org/..
Using rake 10.1.1
Using i18n 0.6.9
Using minitest 4.7.5
Using multi_json 1.9.0
Using atomic 1.1.16
Using thread_safe 0.2.0
Using tzinfo 0.3.39
Using activesupport 4.0.2
Using builder 3.1.4
Using erubis 2.7.0
Using rack 1.5.2
Using rack-test 0.6.2
Using actionpack 4.0.2
Using mime-types 1.25.1
Using polyglot 0.3.4
Using treetop 1.4.15
Using mail 2.5.4
Using actionmailer 4.0.2
Using activemodel 4.0.2
Using activerecord-deprecated_finders 1.0.3
Using arel 4.0.2
Using activerecord 4.0.2
Using encryptor 1.3.0
Using attr_encrypted 1.3.2
Using awesome_print 1.2.0
Using bcrypt 3.1.7
Using bcrypt-ruby 3.1.5
Using net-ssh 2.8.0
Using net-scp 1.1.2
Using tins 1.0.0
Using term-ansicolor 1.3.0
Using sshkit 1.3.0
Using capistrano 3.1.0
Using capistrano-bundler 1.1.2
Using capistrano-rails 1.1.1
Using climate_control 0.0.3
Using cocaine 0.5.3
Using coderay 1.1.0
Using coffee-script-source 1.7.0
Using execjs 2.0.2
Using coffee-script 2.2.0
Using thor 0.18.1
Using railties 4.0.2
Using coffee-rails 4.0.1
Using columnize 0.3.6
Using currencies 0.4.2
Using countries 0.9.3
Using debugger-linecache 1.2.0
Using debugger-ruby_core_source 1.3.2

Gem::Ext::BuildError: ERROR: Failed to build gem native extension.

    /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/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
    --without-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/aaronpardes/.rvm/rubies/ruby-2.1.2/bin/ruby
/Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1573:in `stat': No such file or directory @ rb_file_s_stat - ./212/ruby_debug.h (Errno::ENOENT)
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1573:in `block in fu_each_src_dest'
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1587:in `fu_each_src_dest0'
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1571:in `fu_each_src_dest'
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:399:in `cp'
    from extconf.rb:83:in `block in <main>'
    from extconf.rb:82:in `each'
    from extconf.rb:82:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /Users/aaronpardes/.rvm/gems/ruby-2.1.2@ocx/gems/debugger-1.6.6 for inspection.
Results logged to /Users/aaronpardes/.rvm/gems/ruby-2.1.2@ocx/extensions/x86_64-darwin-13/2.1.0-static/debugger-1.6.6/gem_make.out
An error occurred while installing debugger (1.6.6), and Bundler cannot continue.
Make sure that `gem install debugger -v '1.6.6'` succeeds before bundling.

When I try to run gem install debugger -v '1.6.6' I get the following output:

Building native extensions.  This could take a while...
ERROR:  Error installing debugger:
    ERROR: Failed to build gem native extension.

    /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/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
    --without-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/aaronpardes/.rvm/rubies/ruby-2.1.2/bin/ruby
/Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1573:in `stat': No such file or directory @ rb_file_s_stat - ./212/ruby_debug.h (Errno::ENOENT)
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1573:in `block in fu_each_src_dest'
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1587:in `fu_each_src_dest0'
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:1571:in `fu_each_src_dest'
    from /Users/aaronpardes/.rvm/rubies/ruby-2.1.2/lib/ruby/2.1.0/fileutils.rb:399:in `cp'
    from extconf.rb:83:in `block in <main>'
    from extconf.rb:82:in `each'
    from extconf.rb:82:in `<main>'

extconf failed, exit code 1

Gem files will remain installed in /Users/aaronpardes/.rvm/gems/ruby-2.1.2@ocx/gems/debugger-1.6.6 for inspection.
Results logged to /Users/aaronpardes/.rvm/gems/ruby-2.1.2@ocx/extensions/x86_64-darwin-13/2.1.0-static/debugger-1.6.6/gem_make.out

I am very confused why this error came up all of a sudden. I have been up and running without issue for weeks. I've tried creating a new gemset with rvm and still encounter the same issue. After searching around I found recommendations to update dependencies first and then try bundle install but this did not solve the issue.

Answer 1

Ruby 2.1.2 isn't supported by debugger, unfortunately. Instead, use the byebug gem. See this discussion for more details.

Answer 2

Ruby 2.x is not supported by the debugger gem and you should use byebug instead. Once Rails 4.2.0 is released (or if you use the Rails 4.2.0rc versions) byebug will be the default debugger included in your Gemfile, but if you're on an earlier version of Rails then you'll need to make the change manually in your Gemfile.

Just replace

gem "debugger"

with

gem "byebug"

in your Gemfile and run a bundle install.

Some more background

Even the maintainer of the debugger gem makes this recommendation. The debugger gem's README on GitHub has the following note:

• Only 1.9.2 and 1.9.3 are supported. For 2.X rubies, consider using byebug.

The maintainer has no intention of fixing this; he closed the issue debugger can't be installed on ruby 2.X unfixed, explaining that debugger never properly supported Ruby 2.X and that he now recommends byebug.

Additionally, the maintainer of debugger has not pushed a commit or even replied to a pull request since June 2014. The gem seems to be abandonware at this point.

Rails itself has adopted byebug as the official debugger for Ruby 2.X as of this pull request in April, and from Rails 4.2.0 onwards the Gemfile created when you run rails new my_new_app_name will reference byebug instead of debugger for Ruby 2.X users.

tl;dr

debugger is dead. Use byebug.