Date: Thu, 30 Jan 2003 15:25:28 +0200 (EET) From: Adrian Penisoara <ady@freebsd.ady.ro> To: Erik Trulsson <ertr1013@student.uu.se> Cc: standards@freebsd.org Subject: Re: strftime(): FreeBSD vs. Linux Message-ID: <Pine.BSF.4.10.10301301522001.53987-100000@ady.warpnet.ro> In-Reply-To: <20030130130631.GA69654@falcon.midgard.homeip.net>
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Hi,
On Thu, 30 Jan 2003, Erik Trulsson wrote:
> On Thu, Jan 30, 2003 at 02:15:52PM +0200, Adrian Penisoara wrote:
> > Hi,
> >
> > Recently I had to "backport" a C program written under FreeBSD to
> > Linux and suprisingly I found that the strftime() function behaves
> > different in FreeBSD and Linux: while in FreeBSD strftime() would fill
> > the string buffer with whatever data was specified in the format string
> > up to the specified buffer length, in Linux strftime() would refuse to
> > place the last token specified in the format string if there was not
> > enough space to hold that token and a string terminator (\0).
> >
> > E.g.:
> >
> > #define LEN 12
> > char buffer[LEN+1];
> > time_t t=time(NULL);
> >
> > strftime(buffer, LEN, "%b %d %R", localtime(&t));
> > buffer[LEN] = '\0';
> >
> > printf("Result: [%s]\n", buffer);
> >
> > This snippet would behave as expected in FreeBSD but not in Linux. In
> > Linux you would need to put LEN+1 as the second argument for strftime().
> >
> > I find this to be quite disturbing and I wonder which OS steps on the
> > standards. What is the correct behavior ?
>
> I would suggest you check what the return value from strftime is.
It's zero both on Linux and FreeBSD. It's 12 both on Linux and FreeBSD
when I use LEN+1 as the 2nd argment.
> I suspect in this case it will be 0 for both FreeBSD and Linux, which
> means that the whole string (including the termintating '\0') didn't
> fit in the buffer. If strftime returns 0 the contents of the buffer is
> undefined. (A non-zero return value is the number of characters (not
> including the terminating '\0') that was but into the buffer.
Yep, that's what strftime(2) sais, now that I checked it out.
>
> I.e. it is not really working as you expect in FreeBSD either, but you are
> ignoring the return code that says so.
>
>
> IMO, both systems follow the standard just fine in this case, and the
> bug is in your code.
Yes, you are right. Next time I should RTFM more closely... :-S.
Thanks !
Ady (@warpnet.ro)
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