[bodyfour]

> in that case, a compiler still must set something up to fulfil the main `noexcept` promise - call `std::terminate()`

This is actually something that has been more of a problem in clang than gcc due to LLVM IR limitations... but that is being fixed (or maybe is already?) There was a presentation about it at the 2023 LLVM Developer's meeting which was recently published on their youtube channel https://www.youtube.com/watch?v=DMUeTaIe1CU

The short version (as I understand) is that you don't really need to produce any code to call std::terminate, all you need is tell the linker it needs to leave a hole in the table which maps %rip to the required unwind actions. If the unwinder doesn't know what to do, it will call std::terminate per the standard.

IR didn't have a way of expressing this "hole", though, so instead clang was forced to emit an explicit "handler" to do the std::terminate call

[terrymah]

In MSVC we've also pretty heavily optimized the whole function case such that we no longer have a literal try/catch block around it (I think there is a single bit in our per function unwind info that the unwinder checks and kills the program if it encounters while unwinding). One extra branch but no increase in the unwind metadata size

The inlining case was always the hard problem to solve though