After updating to OS X 10.13.3, I received the following error trying to `require 'vips'`: ``` objc[25602]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. objc[25602]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called. We cannot safely call it or ignore it in the fork() child process. Crashing instead. Set a breakpoint on objc_initializeAfterForkError to debug. ``` Some googling took me to [this post](http://sealiesoftware.com/blog/archive/2017/6/5/Objective-C_and_fork_in_macOS_1013.html), which explains that the error comes from “incorrect code that happened to work most of the time in the past.” I have no way of knowing whether the issue is in `ruby-vips` or `ffi`or `libvips` itself, and I don't really have the time or knowledge to track it down. Using one of that page's suggested workarounds – setting `OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES` in the environment – allowed me to load `ruby-vips` without issue and get on with my work, though I realize I'm just asking OS X to hang later if it encounters a deadlock instead of crashing the process now. I'm reporting it here so there's both an issue to track and a concise explanation and workaround for anyone else who happens to google this error in a `vips` context.