Rachel Kroll
There are more than a few bear traps in the larger Unix environment that continue to catch people off-guard. One of the perennial favorites is thread safety, particularly as it applies to the environment manipulation functions under glibc. The usual warning is that if you run multiple threads, you'd best not call setenv, because if someone else calls getenv, you run a decent chance of segfaulting.
The last time I talked about this was 2017 and I said something goofy like "see you in 2022" at the bottom. Well, it's a little late, but it's come up again, and this time it's biting people who aren't even using C or C++!
Last time, I said that sometimes people run afoul of this by using mktime() which calls getenv()... and then sometimes pick *that* up by using libzip. Here, it's a little different. getaddrinfo() calls getenv(). Did you know that? Before a few minutes ago, I sure didn't! Check out the resolv.conf (5) man page - it looks at LOCALDOMAIN and RES_OPTIONS.
getaddrinfo() is pretty much required if you want to connect to anything beyond mere legacy IPv4 gunk, so it's not like you can avoid it. You're probably going to call it quite often if you are opening connections over the IPv6 Internet.
If you're on Linux, and you're using glibc, you're probably a passenger on this boat. Try not to drill any more holes.
Thanks to Evan for the tip on this one (and good luck with the fix).