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?

Since raise closures don't have their own closure types, the only way is to compare the closure's info pointer against stg_raise_info. This is fine, and we use the same technique in several other places in the RTS. Cheers, Simon