Rails 3.1 and Ruby 1.9.3p125: ruby-debug19 still crashes with “Symbol not found: _ruby_threadptr_data_type” [duplicate]

Answer 1

A fork of ruby-debug just called 'debugger' now exists that incorporates many of the fixes people had been deploying on top of ruby-debug19, so you should be able to just change your Gemfile to

gem 'debugger'

... and off you go.