On 22/09/16 16:03, Jim Meyering wrote: > I was intrigued to see my just-built-from-git gcc fail to compile who.c. > > It's probably too soon to accept a patch like this: in case gcc's > static analysis is going to be improved enough that it can derive the > invariant that the assert makes explicit.
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Maybe gcc can't infer that invariant due to the undefined behavior of signed integer underflow? I.E. if 'when' and 'boottime' were close to TYPE_MINIMUM (time_t). Does gcc 7 avoid the warning if you put this extra condition in the if (bootime... line? && TYPE_MINIMUM (time_t) + 24*60*60 < when > So, perhaps just for reference, for now, here's the patch. > If I were to push it, due diligence would require a post to the gcc > list about this, and (assuming we retain the patch) the addition of a > FIXME-in-2018 comment to see if it is still needed. The assertion looks good to me, though if the above works that would be preferable. thanks, Pádraig
