AFAIK the win32 API is kept backwards compatible by doing exactly as we describe, shipping older versions of the system libraries and automatically using them w

AFAIK the win32 API is kept backwards compatible by doing exactly as we describe, shipping older versions of the system libraries and automatically using them when it's detected that an application needs them. So it's the same thing you call a "hack". Please don't misunderstand, I'm not saying backwards compatibility is bad. But it does cost a non-trivial amount of money and time, it's not just a magic solution to reduce the maintenance cost of something down to zero. If you're doing a cost comparison, that always has to be taken into account. Glibc isn't really a good example, that has a ton of unfortunate broken APIs that should probably be removed entirely (the most notorious example probably being gets) but never will be, and I suspect they will continue to be a source of bugs as long as applications use them and aren't patched. I mean the whole reason musl exists is to get away from some of these maintenance issues in glibc.