Failure to acquire connections on Mac OS within multicore fork()-ed process

[mmuurr]

Failure to acquire connections on Mac OS within multicore fork()-ed process

[gaborcsardi]

The macOS system libraries are not fork safe, so if R or a package calls anything there, that's undefined behavior. External libs might also call these libraries on macOS. E.g. keyring links to the Security framework and sometimes crashes, sometimes it just does not work from a forked process:

❯ keys <- keyring::key_list()
❯ parallel::mclapply(1:4, function(x) keyring::key_list())

 *** caught segfault ***
address 0x110, cause 'invalid permissions'

 *** caught segfault ***
address 0x110, cause 'invalid permissions'

Traceback:
 1: b_macos_list(self, private, service, keyring)
 2: default_backend()$list(service, keyring = keyring)
 3: keyring::key_list()

...

[krlmlr]

Thanks.

IIRC, fork without exec isn't entirely safe on macOS. I forgot the details, but I remember @gaborcsardi shared a compelling example. Can you use multiprocess instead?