Comment by jonhohle
getaddrinfo is defined by POSIX and UNIX. Where the implementation is doesn’t matter. It’s portable, which is why it’s used. The slide deck referenced above talks about better implementations for various platforms, but they are all platform specific.
So OP might not be completely accurate, but getaddrinfo is _the_ way to resolve names if you are writing portable POSIX and/or UNIX code.
Linux and the popular Linux distributions are not POSIX compliant to begin with. Only GNU tries to be, and even GNU adds on a ludicrous amount of extensions because the truth is POSIX isn't good enough.