[tor-bugs] #29640 [Core Tor/Tor]: Improve the monotonic time documentation in compat_time.c

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#29640: Improve the monotonic time documentation in compat_time.c
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 Reporter:  teor                    |          Owner:  teor
     Type:  defect                  |         Status:  needs_review
 Priority:  Medium                  |      Milestone:  Tor: 0.4.1.x-final
Component:  Core Tor/Tor            |        Version:  Tor: 0.2.9.1-alpha
 Severity:  Normal                  |     Resolution:
 Keywords:  tor-time, 040-backport  |  Actual Points:  0.1
Parent ID:                          |         Points:  0.1
 Reviewer:  mikeperry               |        Sponsor:
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Comment (by teor):

 Replying to [comment:2 nickm]:
 > > * on Windows, where the time is not always monotonic, due to an OS bug
 > > * on platforms without specialised monotonic functions, during a wall
 clock time change
 >
 > FWIW, I think our code does some ratcheting to ensure that even if we're
 basing our code on non-monotonic timers, our outputs never move backwards.

 Yes, the code does some ratcheting to make sure that outputs never move
 backwards. But that's not the same as always moving forwards, because the
 result can be zero.

 I separated the ratchet and non-ratchet cases in a fixup, and explained
 them better.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29640#comment:4>
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