Date: Thu, 11 Nov 1999 07:40:01 -0800 (PST) From: "Crist J. Clark" <cjc@cc942873-a.ewndsr1.nj.home.com> To: freebsd-bugs@FreeBSD.org Subject: Re: bin/14817: strptime(3) '%C' conversion incorrect Message-ID: <199911111540.HAA77552@freefall.freebsd.org>
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The following reply was made to PR bin/14817; it has been noted by GNATS.
From: "Crist J. Clark" <cjc@cc942873-a.ewndsr1.nj.home.com>
To: sheldonh@uunet.co.za (Sheldon Hearn)
Cc: FreeBSD-gnats-submit@FreeBSD.ORG, kevin.ruddy@powerdog.com
Subject: Re: bin/14817: strptime(3) '%C' conversion incorrect
Date: Thu, 11 Nov 1999 10:43:26 -0500 (EST)
Sheldon Hearn wrote,
> On Thu, 11 Nov 1999 00:43:29 EST, "Crist J. Clark" wrote:
>
> > However, the '%C' conversion does not work as described in strftime(3)
> > (which strptime(3) references as containing the key for the
> > conversions), nor does a simple 'date +%C' return what the actual
> > strptime(3) function wants.
>
> I think that strptime(3) does behave as expected. I think you're
> assuming too much.
No, it does not. In /usr/src/lib/libc/stdtime/strptime.c we have,
case 'C':
buf = _strptime(buf, Locale->date_fmt, tm);
if (buf == 0)
return 0;
break;
And in stdftime.c we have,
case 'C':
/*
** %C used to do a...
** _fmt("%a %b %e %X %Y", t);
** ...whereas now POSIX 1003.2 calls for
** something completely different.
** (ado, 5/24/93)
*/
pt = _conv((t->tm_year + TM_YEAR_BASE) / 100,
"%02d", pt, ptlim);
continue;
Which quite clearly points out theat strptime(3) is using something
like the _old_ (pre-93!) definition of '%C' contrary to POSIX,
strftime(3) documentation and functionality, and date(1) functionality.
stdptime.c is clearly wrong.
> > struct tm tm;
> >
> > strptime("19","%C",&tm);
> >
> > printf("%d\n",tm.tm_year);
>
> You can't expect tm_year to contain anything sensible after your call to
> strptime, because you haven't given it enough information. Try using it
> in conjunction with %g and you'll get sensible results.
Well, I would go to show that using the existing '%C' combined with
'%g' would not work either, but ran into a little problem. '%g' (or
'%G') is not defined at all in strptime.c.
However, I one might think "%C %y" would accomplish what you would
like. Unfortunately, '%y' _sets_ tm.tm_year, so even if '%C' did
what it was supposed to, the result would be wiped out.
So, now that I look at it more closely, since '%y' cannot be used in
combination with '%C' anyway, '%C' is pretty useless even if it works.
I also now realize if you have a date like, "10/20/50," there is no
way to tell strptime() that you mean 1950 and _not_ 2050. You'd have
to fix tm.tm_year yourself.
It actually might be best to simply elimiate '%C' from strptime.c
altogether (since the current implementation is incorrect and a fix is
almost useless even if it works) and make note of some of these issues
on the manpages.
--
Crist J. Clark cjclark@home.com
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