Re: who.c vs gcc-7's improved buffer overrun check

[Pádraig Brady]

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.

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