I think with c-call you have to tweak some parameter to have them
shown (there was a thread on it previously).
Maybe the new tracer.rb has a clue?

On Sat, Oct 22, 2011 at 5:41 PM, Intransition <transfire / gmail.com> wrote:
> Did something change about `set_trace_func` between 1.8.7 and 1.9.3?
>
> One of my programs quite working. Here is the basic spec:
>
> =A0https://github.com/rubyworks/tracepoint/blob/master/spec/trace.rdoc
>
> This works fine in 1.8.7 but not in 1.9.3.
>
> I'm wondering if I should file a bug report.
>
>