Yo Hal! On Sat, 22 Oct 2016 03:15:01 -0700 Hal Murray <hmur...@megapathdsl.net> wrote:
> >> Word-length mismatch between two programs built under the same OS
> >> never happens, or close enough to never that I don't care.
> > Uh, no. remember when intel OS went from 32 bit to 64-bit? It was
> > a huge issue with ntpd. RasPi is about to have the same
> > problems.
>
> What sort of problem do you expect?
Uh, the one I described in the previous email. Binary C structures
will not match. Pain ensues, just like last time.
> I'd expect troubles if you tried to run a 32 bit gpsd or 32 bit ntpd
> on a 64 bit system (using 32 bit libraries) while the other one was
> 64 bit and the shared struct used int or long rather than int32_t and
> friends.
Ah, so we agree, yes, those configurations will be problematic. We
live through that in the intel 32 -> 64 bit treansition, we are about to
live through it again on the ARM.
> I just checked ntpd/refclock_shm.c
Yeah, ugly, ugly, ugly.
> >> As Hal points out, if you version-number the struct properly you
> >> can add fields at the end ad libitum.
> > IFF you do it right, AND chose a transport that can handle varying
> > lengths. Traditional SHM can not do that. The current NTP SHM can
> > not do that.
>
> The current SHM setup was extended to support nanoseconds without
> breaking old code. (and it doesn't even have a version number slot)
Yeah, but a ton if extensions not done because it would break old code.
RGDS
GARY
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