pathos.helpers.mm.Process.start() not thread-safe on MacOS

[xiay-lcw]

It is probably MacOS problem since the error I got is exactly the same when I try to run os.fork() from multiple threads:

objc[73552]: +[__NSCFConstantString initialize] may have been in progress in another thread when fork() was called.
objc[73552]: +[__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.

Python Version:

Python 3.9.8 (main, Nov 10 2021, 03:55:42)
[Clang 13.0.0 (clang-1300.0.29.3)] on darwin

pathos version: 0.2.9

Works fine on linux.

[xiay-lcw]

Found more information about this:

https://www.reddit.com/r/ruby/comments/72qxjv/comment/dnl8unj/
https://blog.phusion.nl/2017/10/13/why-ruby-app-servers-break-on-macos-high-sierra-and-what-can-be-done-about-it/

Python seems to have swapped to spawn on macOS because of this:
https://github.com/python/cpython/pull/13603/files

[mmckerns]

This issue is with multiprocess, as noted here: uqfoundation/multiprocess#65.