> I don't care about glibc or compatibility with /etc/nsswitch.conf.

So what do you do when you need to resolve system users? I sure hope you don't parse /etc/passwd, since plenty of users (me included) use other user databases (e.g. sssd or systemd-userdbd).

Most software doesn't need to resolve users. You also can always shell out to `id` if you need an occasional bit of metadata.