POSIX lesson please

[Matthew Selsky]

On Mon, Dec 24, 2018 at 03:50:33PM +0100, Achim Gratz via devel wrote:
> Am 24.12.2018 um 11:32 schrieb Hal Murray via devel:
> > You can see POSIX.1-2001, SUSv3, online for free here:
> >      http://www.unix.org/version3/
> 
> I prefer the online version from the Open Group:
> 
> https://pubs.opengroup.org/onlinepubs/9699919799/functions/timer_create.html
> 
> > http://www.unix.org/version3/inttables.pdf has a table that says "tmr" for the
> > timer_xxx functions under the POSIX Base column.  setitimer says xsi in that
> > column.  I assume those are tags for some sort of subset, but I haven't found
> > the descriptions for them and/or what POSIX requires or what we require.
> 
> No, XSI likely refers to the X/Open Systems Interface extension to the ISO C
> Standard.
> 
> http://pubs.opengroup.org/onlinepubs/9699919799/help/codes.html

That's from IEEE Std 1003.1-2017 (which is a revision of 1003.1-2008).  We support 1003.1-2004 per .../devel/hacking.txt

http://pubs.opengroup.org/onlinepubs/009695399/functions/timer_create.html includes a note "TMR" that says:
"The functionality described is optional. The functionality described is also an extension to the ISO C standard."

So timer_create is optional for the minimum POSIX version that we support.


Thanks,
-Matt