Re: [gpsd-dev] gpsd rolls back to 1999

[Greg Troxel]

"Eric S. Raymond" <address@hidden> writes:

> Hal Murray <address@hidden>:
>> 
>> > It does this: Look a half-era ahead.  If that's still less than a reference
>> > date, shift the time stamp forward N cycles for the minimum N that will 
>> > take
>> > it past the reference date.
>> 
>> > I'm not certain what the reference date is, because the context doesn't
>> > exactly match anything in our code.  If it were me writing the code it 
>> > would
>> > be the build date of the instance. 
>> 
>> I don't understand the 1/2 part.  If you have the build date, why throw away 
>> 1/2 the range?
>
> Good question. The main reason I've never tried to fix the wraparound problem
> myself is tha the moere I look at code like this and Perly's black magic,
> the less sure I am that I understand anything.

One issue is how you are really sure that the clock was right when
built.  That's another reason to use a fixed date that is surely in the
past, but I think the notion of reproducible builds (by which I refer to
the notion that the bits built are *exactly* the same on multiple
systems) precludes using build time.  One of the main things to get rid
of when making builds reproducible is any kind of timestamp from the
build environment.