@ronaldoussoren
> I'd prefer to not use vfork on macOS. For one I don't particularly trust that vfork would work reliably when using higher level APIs, but more importantly posix_spawn on macOS has some options that are hard to achieve otherwise and might be useful to expose in subprocess.
I can't comment on vfork() usability on macOS myself, but given the number of issues/considerations described here, I expect that significant research would be needed to check that.
Regarding your second point about extra posix_spawn() options, I actually don't see why it would be an argument against vfork(). Even on Linux, subprocess prefers posix_spawn() to vfork()/fork() when possible, so vfork() support doesn't hinder posix_spawn().