I wrote:
> I didn't try other BSDen; this might be a NetBSD-ism that Apple
> inherited, or maybe it's common among the BSDen.
A bit more research later: OpenBSD behaves like NetBSD, while
FreeBSD behaves like Linux. So that's pretty inconclusive about
what the aboriginal behavior was. I also found that OpenIndiana
behaves like Linux.
For Linux and FreeBSD, it doesn't actually matter to us because
we no longer use SysV semaphores on those platforms. But this
is a live problem on macOS, NetBSD, OpenBSD.
regards, tom lane
