identifying a raise_closure from C

Hi all, In C, I have an StgClosure pointer, pointing to a THUNK. I would like to know whether this particular THUNK is a raise_closure, (as built by raisezh_fast() in rts/Exception.hc). Is there any identifying information I can use to tell definitely whether this THUNK is a raise_closure? Perhaps the stg_raise_info info table has enough information? Thanks heaps, Bernie.