Messages in this thread | | | Date | Thu, 21 Jun 2012 16:10:23 -0700 | From | "H. Peter Anvin" <> | Subject | Re: [tip:perf/core] perf/x86: Add generic Intel uncore PMU support |
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On 06/21/2012 03:51 PM, Andrew Morton wrote: > > What *is* significant is the effect of a signedness change upon > arithmetic, conversions, warnings, etc. And whether such a change > might actually introduce bugs. > > > Back away and ask the broader questions: why did ktime_t choose > unsigned? Is time a signed concept? What is the right thing to do > here, from a long-term design perspective?
Time is definitely a signed concept -- it has no beginning or end (well, the Big Bang, but the ±110 Myr or so uncertainty of the exact timing of the Big Bang makes it a horridly awkward choice for epoch.)
Now, for some users of time you can inherently guarantee there will never be any references to time before a particular event, e.g. system boot, in which case an unsigned number might make sense, but as a whole I think using a signed type as time_t in nearly all Unix implementation was The Right Thing.
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