Not work on macOS Mojave: may have been in progress in another thread when fork() was called.

[fifiteen82726]

forecast = ForecastIO.forecast(37.8267, -122.423)
objc[1684]: +[__NSPlaceholderDictionary initialize] may have been in progress in another thread when fork() was called.
objc[1684]: +[__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.

[enciie]

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

[swaathi]

This fix doesn't work on Mojave. It does the trick on High Sierra though.

[ghost]

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

run this in terminal

[fblupi]

Same problem here. Even adding the env variable above

[sourabharsh]

It worked

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

run this in terminal

It worked for me on Mojave. thanks a lot!

[reekoong]

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

Worked for me

[marc-wilson]

Running

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

does not work on Mojave

[marc-wilson]

Not to revert my previous comment, but I actually did get the export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES environment variable to work. The problem was that I was running the command in the terminal. It won't work there.

In my case, I use PyCharm with a virtual environment. After adding the environment variable directly in my build/debug configuration under environment variables, it worked like a charm:

I'm not sure if this is something that's specific to my setup, but doing it this way worked for me.

[coisnepe]

Doesn't seem to work in Catalina...

[jakubmuransky]

Doesn't seem to work in Catalina...

Same here, stop working on catalina, stuck on Gathering Facts

[gbudiman]

FWIW, I landed on this page while googling the exact same error message caused by different gem (google-cloud-ruby). I downgraded ruby from 2.6.5 to 2.6.3 and the error went away. I'm on Catalina. Take this with a bucketload of salt though.

[benkruger-neyborly]

Super stuck with this with Catalina :(

[Arpanbhalla]

Stuck with Catalina too

[simonc]

Hi. I had a similar issue after upgrading some brew packages. I couldn't run puma or rspec and was getting this error.

I destroyed my installed rubies and gems and recompiled Ruby. I'm not getting the error anymore.

Hope it helps some of you ❤️

[jatin-ch]

worked for me on Mojave

$ nano .bash_profile
Add the following line to the end of the file:

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

Save, exit, close terminal and re-open the terminal.

https://stackoverflow.com/questions/50168647/multiprocessing-causes-python-to-crash-and-gives-an-error-may-have-been-in-progr/52230415

[danielrg]

Try running this way:
OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES rails s

[dennyf]

Same issue here after upgrading to Catalina.

export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES
did not work for me.

I was experiencing the issue with an old project running Ruby 2.4.4 (it was not happening with a new project that I created using ruby 2.6.5).
@simonc advice worked for me - I reinstalled ruby 2.4.4 and all the gems in my gemset. For some reason though, reinstalling the gems by deleting them and running bundle install did not work for me. However after I ran bundle update , the issue got resolved.

[noahleal]

I had this issue today after a fresh install of Catalina. In the end it took upgrading command line tools and restarting my computer to fix it! ✨

[noahleal]

Well, that only worked for a few days actually. Now I am getting the same error

[mcdave029]

• MacOS Catalina
• asdf version manager
• zsh

Works for me https://stackoverflow.com/a/53404317 turns out I just need to put OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES above my version manager in .zshrc

[benkruger-neyborly]

To fix the issue

rvm implode
\curl -sSL https://get.rvm.io | bash
rvm install 2.4.9

[tlkiong]

Just happened to me on Ruby 2.6.5.
Nothing solves it.

This issue is honestly ridiculous

[mozulevskyi]

Worked for me on Catalina 👍 Thanks a lot.
vim .bash_profile, and add this line before the last one.
export OBJC_DISABLE_INITIALIZE_FORK_SAFETY=YES

[[ -s "$HOME/.rvm/scripts/rvm" ]] && source "$HOME/.rvm/scripts/rvm"

[IlyaUmanets]

Try this one
export DISABLE_SPRING=true
If solutions above don't work for you