getaddrinfo_a uses a thread to call getaddrinfo asynchronously. However, as far as I can tell this means it still has all the same caveats as getaddrinfo. Notably, it will result in a getenv call, making it unsafe if another thread concurrently touches the environment. Given this, I *think* it would make sense for getaddrinfo_a to be marked "MT-Safe env locale" just like getaddrinfo. This would make sure people know that getaddrinfo_a does not avoid the thread-safety issues of getaddrinfo. - Josh Triplett
