@RAOF There are several different not-compatible EH regimes on different platforms, some DW2-like and some SEH-like. Plus there are callers that are just totally EH-unaware (most C host programs) so it's a nice idea to model panics for them _somehow_.

But even FFI-aside, the perf and codegen bits are sufficiently subtle that (eg.) Swift made its own LLVM calling convention (with pinned error register) for error-returns.