I've just been having another look at this, and the simplest solution appears to be to just use the default language dialects, without providing specific command-line arguments. On Linux, using a recent version of gcc (gcc --version, probably 13), the default dialect is gnu17 (which provides your getaddrinfo()). On macOS, using a recent version of clang (clang --version, probably 15), the default dialect is c11 (which also provides your getaddrinfo(), because Apple love to bundle everything in). So, the best approach on either platform seems to be to just run cc without any options for the language standard/dialect.