This doesn't seem correct to me
You are right, its incomplete, but it also was based on the logic already in MSVCRT_vswprintf_s, which is just as incomplete!
I'll happily just raise a bug report if the patch is insufficient, but in general all the _s special processing is missing from the printf* family, and the patch implements enough to get the basic functionality working. I probably should have put a fixme comment in like MSVCRT_vswprintf_s though but would that be enough?
Jason