And I agree. The idiom remains possible, it just doesn't need to me mentioned / encouraged.
Ingo Schwarze <schwa...@usta.de> wrote: > Hi Scott, > > Scott Cheloha wrote on Fri, Aug 17, 2018 at 10:20:09AM -0500: > > > I don't think we should encourage or even mention the possibility of the > > use of poll(2) to effect millisecond timeouts. Even if the standard > > library lacks such an interface. > > > > I'm pretty sure you can't use this hack portably, either. > > > > But mostly I just think it's a misuse of the interface and potentially > > confusing to a reader of such code: > > Nowadays, POSIX has nanosleep(2). Before that, XPG had the now > obsolete usleep(3) that appeared in 4.3BSD, but which never made > it into POSIX. Before nanosleep(2) became firmly established, using > select(2) for portably sleeping less than a second was common IIRC. > So the reason for the recommendation may be that poll(2) intends > to replace select(2). > > I agree that recommending poll(2) for the functionality of nanosleep(2) > no longer makes sense. > > Note that your diff also removes the information about what happens > when fds == NULL. If i read it correctly, POSIX does not specify > that, so you may be right that there might be some system out there > where it doesn't work. > > Leaving behaviour that is unspecified by the standard unspecified > in the manual page is often a good idea, unless we specifically > want to support it as an extension. Guaranteeing such an extension > does not seem useful to me in the present case. > > So, your diff is OK schwarze@, but i think you need another OK from > a developer who is more familiar with networking or low-level I/O. > > Yours, > Ingo > > > > Index: lib/libc/sys/poll.2 > > =================================================================== > > RCS file: /cvs/src/lib/libc/sys/poll.2,v > > retrieving revision 1.35 > > diff -u -p -r1.35 poll.2 > > --- lib/libc/sys/poll.2 14 Feb 2017 17:51:14 -0000 1.35 > > +++ lib/libc/sys/poll.2 17 Aug 2018 14:55:48 -0000 > > @@ -183,12 +183,6 @@ and > > flags may be used to detect when out-of-band socket data may be read > > without blocking. > > .Pp > > -In addition to I/O multiplexing, > > -.Fn poll > > -can be used to generate simple timeouts. > > -This functionality may be achieved by passing a null pointer for > > -.Fa fds . > > -.Pp > > The > > .Fn ppoll > > function is similar to >
