Trace dynamic library calls of ruby C extension

Question

For debugging purposes I want to get some call traces of a ruby app which uses an extension library to interface with a C lib. I found http://unroller.rubyforge.org/ which has nice output but not for the library calls.

I want ltrace for ruby extensions.

thx

Update: I'm after a bug and don't know if its the ruby extension or external library thats causing it. So the whole trace including variable references would be nice