call_stack 0.1.0: making ruby-breakpoint/Rails’ breakpointer work with Ruby 1.8.5

Ruby 1.8.5 has been out for a couple weeks and broke Binding.of_caller and Rail’s breakpointer. I’d promised I’d provide a workaround, and I finally wrapped it up.

I’ve just released call_stack: backtrace data and 1.8.5-safe breakpoint/Binding.of_caller, which provides an alternative Binding.of_caller implementation and some additional functionality to obtain backtrace information (the “call stack”). You can override a pre-existent binding_of_caller.rb by loading breakpoint185.rb:

 ruby -rbreakpoint185 myapp.rb

Here’s how you’d use it with Rails’ breakpointer:

1. put the breakpoint calls in the code you’re inspecting, as usual
2. start the “breakpointer” as usual with script/breakpointer
3. run the application with ruby -rbreakpoint185 script/server

  RubyGems caveats

If you’ve installed call_stack with RubyGems, -rbreakpoint185 will not work (RubyGems cannot handle -rlib options passed to ruby yet), and you’ll have to do something like:

 ruby -e "require 'breakpoint185'; load 'script/server'"

(assuming you’ve set RUBYOPT=-rubygems, otherwise prepend it to the above line or add require ‘rubygems’)

  Word of caution

Loading breakpoint185 will slow down your application a bit, since it uses a C event hook to record the binding and additional information on each method call, so it should only be used when debugging/inspecting some code.

call_stack was built with bits of code from an abandonned rcov: code coverage for Ruby branch, but in the future it might rely on Kent Sibilev’s ruby-debug for the low-level work.