Yo Eric! > > > Would it help to have another signed type? > > > > The short answer is "no". The longer answer: > > I'm starting to disagree, I see a need for only a signed type. > > Too often the unsigned type is then used to compute offsets and the > casts get ugly.
Gack... I gotta do a quick U-turn on this. I found some pretty hidden
assumptions that I did not expect in the code. Assumptions that I will
document, in the code, for the next poor soul that looks at this.
I had assumed, and code does not document, that l_fp was sometimes
used as like a timespec (time_t seconds and nanoseconds UNIX epoch).
Since time_t is signed, it can also be used as an offset of seconds and
nanoseconds. But is is also used to represent NTP time which uses
a base apoch of 12/1/1 BC!
A signed l_fp is just fine for POSIX time, until overflow at 0x7fffffff,
which is decimal 2147483747 seconds, the dreaded "Mon Jan 18 19:15:47
PST 2038"
To convert POSIX time to NTP time you add 0x83aa7e80 (decimal 2208988800).
Note that number does not fit is a 32 bit type, signed or unsigned.
As I write this, the time now is POSIX: 1489094096. As NTP time it
is 3698082896 (0x160ad3a8). Notice that is 33 bits!
Sure ntpd is working now, but it is doing so using overflow arithmetic!
I only had to look at the clang output for a month to see this.
Please ponder that again: ntpd is using overflow arithmetic! No wonder
the code is so touchy.
I see 12 uses of this in the code, so fixable, but I'll need to stare
at my navel a bit longer for enlightenment...
RGDS
GARY
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Gary E. Miller Rellim 109 NW Wilmington Ave., Suite E, Bend, OR 97703
g...@rellim.com Tel:+1 541 382 8588
Veritas liberabit vos. -- Quid est veritas?
"If you can’t measure it, you can’t improve it." - Lord Kelvin
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