Resource leaks, crossing non-exception-safe library/system code, CPU-specific quirks like accidentally unrestored FP/vector/control state, etc. Granted it's always been highly system-specific stuff, but that's the worst kind.

Gotcha, that’s a good list.

It’s true that Fil-C doesn’t try to protect you from those bugs. I just don’t think of those as the worst things that can happen when you misuse these APIs.