Is a bracket-like construct for signal handlers possible?

I'd like to be a good Unix citizen and restore the signal handlers to the way they were before I meddled with them. Without necessarily ending the process. But all I found that could be used to that effect is `installHandler`; and while it does provide the former handler, I'm at a loss as to what to restore `iset` to.

```Haskell
installHandler :: Signal -> Handler -> Maybe SignalSet -> IO Handler
installHandler int handler iset = oldhandler
```

Peeking at the `sigaction(3)` manpage made matters worse :-) as there's seemingly an additional `sa_flags` bitset that ought to be restored as well and doesn't appear to be exposed by the current API.