Date: Sun, 3 Jun 2001 10:53:11 +0200 From: Erik Trulsson <ertr1013@student.uu.se> To: arch@FreeBSD.ORG Subject: Re: time_t definition is wrong Message-ID: <20010603105311.A34715@student.uu.se> In-Reply-To: <20010603011621.A88949@dragon.nuxi.com>; from obrien@FreeBSD.ORG on Sun, Jun 03, 2001 at 01:16:21AM -0700 References: <200106012318.f51NI8w38590@bunrab.catwhisker.org> <20010602085237.A73968@dragon.nuxi.com> <200106021739.f52Hd9V03943@earth.backplane.com> <p05100e0fb73ee9d458f7@[128.113.24.47]> <200106022043.f52KhFh35078@vashon.polstra.com> <20010603011621.A88949@dragon.nuxi.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Sun, Jun 03, 2001 at 01:16:21AM -0700, David O'Brien wrote:
> On Sat, Jun 02, 2001 at 01:43:15PM -0700, John Polstra wrote:
> > I'd prefer to keep it as "long" at least on the i386, because that's
> > what the type was for years before ANSI renamed it to "time_t".
>
> We will have to special case all of our code that uses time_t and
> printf() since our 64-bit types will be "%d", not "%ld", and we'll have
> to hope all the i386 users remember that when they change things in
> /usr/src/. I still think it is better to use a consistent time_t
> definition (and printf format specifier) across all FreeBSD platforms.
>
> But if the wind is really swaying that way... I'll concede.
Code that uses time_t should be written to work regardless of if time_t
is defined as 'long', 'int' or 'short' (the last last one is a bit
unlikely though :-) )
So if one has
time_t t;
then both printf("%d",t) and printf("%ld",t) are wrong and should be fixed.
Programmers making unwarranted assumptions about the size of time_t and
the corresponding printf format specifier should get a clue or two and
stop doing that.
The correct thing to do is printf("%ld",(long)t) which will work just
fine with both ints and longs.
If one has C99-aware headers/libraries then the correct thing to do is
printf("%jd",(intmax_t)t) which will work for all signed integer types.
Although the C standard allows time_t to be any arithmetic type I think
one can safely assume that it will be a (signed) integer type on Unix
systems (including FreeBSD).
On i386 everything should work fine regardless of whether time_t is
defined as 'int' or 'long' as long as they are both 32-bit.
The worst that can happen is some (well-deserved) compiler warnings.
Eventually time_t will have to be changed to a 64-bit type but then it
will probably be spelled 'long long' (or, preferably, int64_t assuming
FreeBSD has C99-compatible header files by then.)
(Changing the size of time_t, especially if time_t no longer could fit
n a 'long', will almost certainly break lots of programs and require
quite a bit of work to fix.)
--
<Insert your favourite quote here.>
Erik Trulsson
ertr1013@student.uu.se
To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?20010603105311.A34715>