According to this post... http://www.sealiesoftware.com/blog/archive/2017/6/5/Objective-C_and_fork_in_macOS_1013.html
The rules around initialize and fork() have changed in macOS 10.13, which is coming out in a month or so. I tried using Unicorn today to run a unicorn_rails instance, and got this as part of my traceback: objc[95737]: +[__NSPlaceholderDictionary 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. E, [2017-08-04T08:35:28.148339 #95531] ERROR -- : reaped #<Process::Status: pid 95736 SIGABRT (signal 6)> worker=1 I'm not sure if this is something downstream, but I thought I'd bring it to your attention. My temporary solution is to preface my commands with OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES. Jeffrey
