On 17/11/14 12:41, Corinna Vinschen wrote:
On Nov 15 16:56, David Stacey wrote:
I'm not convinced that the test is valid. Poco seems to be making
assumptions about clock_gettime() and gettimeofday() that simply aren't
guaranteed to hold - but obviously do in Fedora at least. For instance, the
test must be assuming that either the accuracy of the two routines is
identical, or be making assumptions about rounding in the less accurate
routine.
I think it would be better to patch the test so that it uses clock_gettime()
exclusively (and not gettimeofday() at all), and then this problem will
disappear. But I thought I would submit it here to see what you thought
before raising a ticket with the Poco developers.
What do you think?
Same as you. One problem is that CLOCK_REALTIME (which is the one used
by gettimeofday) is not monotonic by definition, see for instance the
Linux man page:
This clock is affected by discontinuous jumps in the system time
(e.g., if the system administrator manually changes the clock), and by
the incremental adjustments performed by adjtime(3) and NTP.
The second problem, and that's the one affecting this testcase mostly,
is the accuracy of the timer (see clock_getres function).
Thank you for confirming my suspicions. I'll patch the test and roll a
poco-1.4.7 later in the week. I'll also raise a ticket and get this
fixed upstream.
Thanks once again,
Dave.
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