New config feature - time1 can declare GPS wraparound compensation

Sanjeev Gupta ghane0 at gmail.com
Fri Aug 16 18:03:50 UTC 2019


Eric,

On a 32-bit debian:

[ 73/101] Compiling ntpd/ntp_io.c
../../ntpd/ntp_scanner.c: In function ‘yylex’:
../../ntpd/ntp_scanner.c:40:30: warning: integer overflow in expression of
type ‘long int’ results in ‘659554304’ [-Woverflow]
 #define GPS_ERA_13BIT (8192L * SECONDS_IN_WEEK)
                              ^
../../ntpd/ntp_scanner.c:940:20: note: in expansion of macro ‘GPS_ERA_13BIT’
      era_offset += GPS_ERA_13BIT;
                    ^~~~~~~~~~~~~
-- 
Sanjeev Gupta
+65 98551208     http://www.linkedin.com/in/ghane


On Sat, Aug 17, 2019 at 1:41 AM Eric S. Raymond via devel <devel at ntpsec.org>
wrote:

> I've just pushed a change that interprets a 'g' suffix on a clock time1
> fudge option as an instruction to add the number of seconds in a
> 1024-week GPS era. There can be more than one g. Using this, you can
> compensate for era rollover in old GPS devices.
>
> Credit to James Browning for the idea. It's actually done at the
> scanner level, so it will work for other double-valued options such
> as the time2 fudge - not that I expect that to be used.
>
> If you have a GPS old enough to require wraparound compensation,
> please test; I don't think I do anymore.
>
> I've also updated the driver documentation, pointing out where this
> option is likely to be of use, and the NEWS file.
>
> Mark: once we've tested this it might merit a point release.
> --
>                 <a href="http://www.catb.org/~esr/">Eric S. Raymond</a>
>
> You know why there's a Second Amendment?  In case the government fails to
> follow the first one.
>          -- Rush Limbaugh, in a moment of unaccustomed profundity 17 Aug
> 1993
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