On Mon, 18 Jul 2005 17:34:55 +0200, Campo Weijerman <[EMAIL PROTECTED]> wrote:
> > + /* This edge case is to workaround the undefined behaviour, where the
> > + * TIMEZONE makes the time go beyond the defined range.
> > + * gmtime (0x7fffffff) => 2038-01-19 03:14:07
> > + * If there is a negative offset in TZ, like MET-1METDST, some broken
> > + * implementations of localtime () (like AIX 5.2) barf with bogus
> > + * return values:
> > + * 0x7fffffff gmtime 2038-01-19 03:14:07
> > + * 0x7fffffff localtime 1901-12-13 21:45:51
> > + * 0x7fffffff mylocaltime 2038-01-19 04:14:07
> > + * 0x3c19137f gmtime 2001-12-13 20:45:51
> > + * 0x3c19137f localtime 2001-12-13 21:45:51
> > + * 0x3c19137f mylocaltime 2001-12-13 21:45:51
> > + * Given that legal timezones are typically between GMT-12 and GMT+12
> > + * we turn back the clock 23 hours before calling the localtime
> > + * function, and add those to the return value. This will never cause
> > + * day wrapping problems, since the edge case is Jan *19*
> > + */
> > + T = *tp - 82800; /* 23 hour. allows up to GMT-23 */
> > + P = localtime (&T);
> > + P->tm_hour += 23;
> > + if (P->tm_hour >= 24) {
> > + P->tm_hour -= 24;
> > + P->tm_mday++;
> > + }
>
> Well, it's not nice, but I suppose it should fix the boundary case.
> However, I think you should also increment these other fields along
> with tm_mday:
>
> int tm_wday; /* Day of week (Sunday = 0) */
> int tm_yday; /* Day of year (0 - 365) */
Both done now in #25173
> I'm not fond of this sort of struct tm manipulation. It's easy to
> get wrong, and then you have just replaced a known bug by an unknown
> one. Luckily, 2038-01-19 is supposed to be on a Tuesday, and we
> are sufficiently far away from the boundaries of the week, month, and
> year... Until someone starts using TZ=CUT-50, say :-(
As the surrounding comments already said.
By the time this workaround should be a problem, we are all on 64, 128 or
even 256 bit machines
As you can see, the bug is already safe for 64bit values, since the
workaround only acts in a small window:
+ if (!tp || *tp < 0x7fff573f || *tp >= 0x80000000)
+ return (localtime (tp));
--
H.Merijn Brand Amsterdam Perl Mongers (http://amsterdam.pm.org/)
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