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From: ado@elsie.UUCP
Newsgroups: net.unix-wizards
Subject: Re: 4.2BSD ctime() arguments
Message-ID: <872@elsie.UUCP>
Date: Mon, 16-Apr-84 11:15:07 EST
Article-I.D.: elsie.872
Posted: Mon Apr 16 11:15:07 1984
Date-Received: Tue, 17-Apr-84 07:44:57 EST
References: <398@noscvax.UUCP>, <3741@utzoo.UUCP>
Organization: NIH-LEC, Bethesda, MD
Lines: 48

Henry Spencer notes:
	. . .The argument to gmtime() should be of type "time_t",
	and ***ONLY*** time_t.  Just exactly what kind of int time_t is, is
	something that is machine-dependent and system-dependent; you are not
	supposed to imbed such assumptions into your programs!

	The manual page is a bit out of date.  The lint library is correct.
	The include file is machine-dependent and 4.2BSD-dependent. . .it
	*should* have been "typedef long time_t"!  It makes no actual difference
	on the VAX, but it makes the portability situation a lot clearer.
	There are a *LOT* of Unix machines where time_t is not int. . .

The "ctime" manual page on our 4.1 system has "7th Edition" in the
lower-left-hand corner.  I suspect that on "7th Edition" systems the way to call
"ctime" is STILL with a "long *".  I don't know if the "sys/types.h" file in
which "time_t" is "typedef"d is even present on "7th edition" systems.
Is there anyone out there who does?
(And what's the situation on System V with respect to the "ctime" argument?)

On our 4.1 system, the lint library (or the "ctime" source code, take your
pick) is wrong.  The lint library claims that "ctime" takes a "time_t *" as
its argument, where "time_t" has been "typedef"d to be an "int". 
But "ctime.c" reads (in part):
	char *
	ctime(t)
	long *t;
	{ . . .
which says that "ctime" takes a "long *" as its argument.
Maybe this discrepancy has been fixed in 4.2bsd.
Then again, maybe it has been replaced with a new discrepancy.
Can anyone running 4.2 shed light on this?

The bottom lines:  to keep "lint" happy and ensure portability, I'd do this:
	#ifdef vax
	#include <sys/types.h>
	time_t	timearg;
	#else
	long	timearg;
	#endif

--
UNIX is an AT&T (or Bell Labs, or AT&T Bell Labs) trademark.
(Can some AT&T mouthpiece post the preferred form for this note?)
VAX is a Digital Equipment Corporation trademark.
TIME is a Time/Life, Incorporated trademark.
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