[LEAPSECS] LEAPSECS Digest, Vol 82, Issue 6

Joseph Gwinn joegwinn at comcast.net
Sun Aug 11 14:40:37 EDT 2013

On Sun, 11 Aug 2013 14:21:41 -0400, Greg Hennessy wrote:


>> The POSIX standard in fact forbids it, precisely to escape the time

>> wars.


> If the guys writing POSIX think that forbidding POSIX from matching

> reality means no time wars, I think they have another think coming.

No, we already had the time war. Twice. It's a very long story,
documented in the TimeNuts archive, which in turn points to the noisy
debates in the POSIX world.

>> However, POSIX allows an implementation (read, operating system) to

>> define as many named clocks as desired.


> I have never head of this before. How does one define a (for example)

> UTC clock in a POSIX system?

As a user, you do not. As a platform developer such as Linux kernel
developer, you can.

Here is some debate about two named clocks in POSIX/Linux:

The general interface used by these two named clocks can be extended by
a kernel developer.

At this point, people usually ask why this could not also be provided
to the user. The problem is that one cannot just whistle a new kind of
clock up. The hardware and kernel must support it, and these things
cannot be provided by a user.

Joe Gwinn

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