THIS IS VERY-VERY EXPERIMENTAL AND HACKISH. USE ON YOUR OWN RISK.
It adds Thread#backtrace. Although I abuse private APIs of Ruby, no ruby patches are required. It does not work with 1.9.
Installation is simple as
gem install thread_backtrace >> require 'thread_backtrace' => true >> def a; b; end; def b; c; end; def c; sleep 10; end => nil >> Thread.fork{a }.backtrace => ["(irb):2:in `c'", "(irb):2:in `b'", "(irb):2:in `a'", "(irb):3:in `irb_binding'", "(irb):3:in `fork'", "(irb):3:in `irb_binding'", "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/workspace.rb:52:in `irb_binding'", "/System/Library/Frameworks/Ruby.framework/Versions/1.8/usr/lib/ruby/1.8/irb/workspace.rb:52"] Also it adds caller_for_all_threads method to kernel. But it's not the same as output of REE (it doesn't skip the first entry for the current thread).