The rules for using Objective-C between fork() and exec() have changed in macOS 10.13. Incorrect code that happened to work most of the time in the past may now fail. Some workarounds are available. fork() and Objective-C Before macOS 10.13, the Objective-C runtime did not support use between fork() and exec() in the child process of a multithreaded parent process. Calling any Objective-C method i