Feature or enhancement

Proposal:

macOS supports a non-standardposix_spawn() flag,POSIX_SPAWN_CLOEXEC_DEFAULT, which makes "only file descriptors explicitly created by the file_actions argument available in the spawned process; all of the other file descriptors are automatically closed in the spawned process."

This would be useful forsubprocess, whereclose_fds defaulting to True means thatposix_spawn() is not used by default.POSIX_SPAWN_CLOEXEC_DEFAULT combined with (the also non-standard)posix_spawn_file_actions_addinherit_np() would provide a correct way to useposix_spawn() whenclose_fds=True.

AChromium bug indicates thatPOSIX_SPAWN_CLOEXEC_DEFAULT was added in OS X 10.7 but causes kernel panics there, for safety this should probably only be used on OS X 10.8 and later.

This could be added as acloexec_default=False argument toos.posix_spawn() andos.posix_spawnp().

Has this already been discussed elsewhere?

This is a minor feature, which does not need previous discussion elsewhere

Links to previous discussion of this feature:

#79718 was the original issue for usingos.posix_spawn() insubprocess.
#86904 proposed changingclose_fds to default to False, soposix_spawn() could be used more often