GNU libc has a lot to answer for here honestly.
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How does the Linux kernel maintaining backward compatibility stiffle UX innovation?
But sometimes a user is an api consumer.
There’s plenty of horrible kernel functions with footguns in Linux, but they won’t be improved due to “never break userspace”
theres lots if examples if you need specifics. readdir, epoll, futumesat (and ufutumesat), etc.