I think the case of Windows is slightly different. Its architecture has the same backwards compatibility challenges of GNU libc, but where GNU took a user-hosti

I think the case of Windows is slightly different. Its architecture has the same backwards compatibility challenges of GNU libc, but where GNU took a user-hostile approach ("just recompile"), Microsoft invested thousands of person-years to mitigate and resolve issues as they were discovered. Most folks reading this are likely familiar with Raymond Chen's blog posts about compatibility shims for older binaries, or stories like the Windows 95 work around for memory-management bugs in SimCity. That's the kind of thing that happens when you design an OS ABI with problems, but are committed to bearing the cost of those problems yourself rather than passing them along to users. I'm sure if you asked today's Windows team if they'd have a different approach, they'd rattle off a half-dozen great ideas for backwards-compatible syscall ABIs. There's been lots of research in that area since the foundations of our current OS ecosystem were laid down 30 years ago.