Johannes Schindelin <Johannes.Schindelin@xxxxxx> writes:
>> Eh, sorry, but why?
>
> The thing is: I want to prevent invalid dates in gc.pruneExpire from going
> unnoticed, _especially_ since they would default to "now". IOW if you
> said something like "one.weak.ago", it would actually have the same effect
> as "now" and offer _no_ grace period.
>
> But like you said, comparing the difference of two unsigned longs to >= 0
> might be quite stupid. Instead, I compare them _directly_.
>
> Since I compare the value to "now" first, and only if it is not, compare
> the approxidate() of the value to the current time stamp, I can verify
> that no invalid date was specified.
>
> Unfortunately, this check includes future dates. Fortunately, they do not
> make sense at all.
>
> To make my reasoning clear, how about this comment above that if() clause?
>
> /*
> * In case of an invalid date, approxidate() returns the
> * same as approxidate("now"). Since the millisecond
> * boundary could have been crossed between the two calls
> * to approxidate(), we compare not only for equality,
> * but also if the former is greater than the latter.
> *
> * Note: this assumes that future dates are invalid, which
> * makes sense, really.
> */
>
> Hmm?
Ah,...
But C language rules haven't changed in such a way that it guarantees B to
be evaluated before A when you write "A >= B", have it?
So at least I think you would need something like this if you go that
route:
if (strcmp(value, "now")) {
unsigned long now = approxidate("now");
if (approxidate(value) >= now)
return error("Invalid %s: '%s'", var, value);
...
}
Also the resolution of approxidate() is in seconds so millisecond boundary
does not matter, but that issue is, eh, secondary ;-).
I have to wonder if approxidate_with_error() function that takes a pointer
to receive an error condition may be a better way to solve this cleanly.
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