Rails with ruby-debugger throw 'Symbol not found: _ruby_current_thread (LoadError)'

Question

I have standard ruby-head and Rails 3.1rc4. I installed ruby-debug with following instructions from http://dirk.net/2010/04/17/ruby-debug-with-ruby-19x-and-rails-3-on-rvm/<

Answer 1

My system is rvm 1.18.10 and ruby 1.9.3p392 on Mac OSX 10.8.5. I first installed gem 'ruby-debug19', but for the well-known reason, the debugger did not work.

I then ran

local$ gem install 'debugger'

as suggested by many other posts. The gem was installed successfully with the following outputs:

local$ gem install debugger
Fetching: debugger-ruby_core_source-1.2.3.gem (100%)
Fetching: debugger-linecache-1.2.0.gem (100%)
Fetching: debugger-1.6.2.gem (100%)
Building native extensions.  This could take a while...
Successfully installed debugger-ruby_core_source-1.2.3
Successfully installed debugger-linecache-1.2.0
Successfully installed debugger-1.6.2
3 gems installed
Installing ri documentation for debugger-ruby_core_source-1.2.3...
Installing ri documentation for debugger-linecache-1.2.0...
Installing ri documentation for debugger-1.6.2...
Installing RDoc documentation for debugger-ruby_core_source-1.2.3...
Installing RDoc documentation for debugger-linecache-1.2.0...
Installing RDoc documentation for debugger-1.6.2...
local$ irb
1.9.3-p392 :002 > require 'debugger'
=> true

I then ran

local$ rails server --debug
/usr/local/rvm/gems/ruby-1.9.3-p392/gems/activesupport-3.2.11/lib/active_support/dependencies.rb:251:
in`require': dlopen(/usr/local/rvm/gems/ruby-1.9.3-p392/gems/ruby-debug-base19-0.11.25/lib/ruby_debug.bundle,
9): Symbol not found: _ruby_current_thread (LoadError)
Referenced from: /usr/local/rvm/gems/ruby-1.9.3-p392/gems/ruby-debug-base19-0.11.25/lib/ruby_debug.bundle
Expected in: flat namespace
 in /usr/local/rvm/gems/ruby-1.9.3-p392/gems/ruby-debug-base19-0.11.25/lib/ruby_debug.bundle - /usr/local/rvm/gems/ruby-1.9.3-p392/gems/ruby-debug-base19-0.11.25/lib/ruby_debug.bundle
......

I resolved this error by commenting out the line "gem 'ruby-debug19'" and adding a new line "gem 'debugger'" in the Gemfile, and then ran

local$ bundle update

After that, everything worked fine.

local$ rails server --debug
=> Booting WEBrick
=> Rails 3.2.14 application starting in development on http://0.0.0.0:3000
=> Call with -d to detach
=> Ctrl-C to shutdown server
=> Debugger enabled
[2013-10-15 12:50:21] INFO  WEBrick 1.3.1
[2013-10-15 12:50:21] INFO  ruby 1.9.3 (2013-02-22) [x86_64-darwin10.8.0]
[2013-10-15 12:50:21] INFO  WEBrick::HTTPServer#start: pid=7206 port=3000