"Real C" for the scope of this thread is defined (by me) as code compiled by a C compiler in contrast to an `extern "C"` function that is compiled by a C++ compiler. E.g. gcc by default does "The Right Thing" (`-fexceptions`) for C++ code, but not for C code. That's why I made the distinction. In theory it isn't needed, because the behavior is undefined by the C++ and C standards in both cases.
`lua_pcall()` (C++) -> Lua code -> `lua_CFunction` (`extern "C"`) -> `lua_error()` (C++) -> `throw`.
So we have undefined behavior
Whether it works in practice depends on compiler/implementation, command line flags, whether it's "real C" code the exception is passing through, etc.