Thomas Munro <thomas.munro@gmail.com> writes:
> The reason we need it for macOS is that they have had fdatasync
> function for many years now, and configure detects it, but they
> haven't ever declared it in a header, so we (accidentally?) do it in
> c.h. We didn't set that up for Apple! The commit that added it was
> 33cc5d8a, which was about a month before Apple shipped the first
> version of OS X (and long before they defined the function). So there
> must have been another Unix with that problem, lost in the mists of
> time.
It might have just been paranoia, but I doubt it. Back then we
were still dealing with lots of systems that didn't have every
function described in SUS v2.
If you poked around in the mail archives you could likely find some
associated discussion, but I'm too lazy for that ...
regards, tom lane