Path: utzoo!utgpu!water!watmath!clyde!att!osu-cis!tut.cis.ohio-state.edu!bloom-beacon!mit-eddie!uw-beaver!tektronix!tekcrl!terryl
From: terryl@tekcrl.TEK.COM
Newsgroups: comp.unix.wizards
Subject: Re: #defines with variable # arguments
Message-ID: <2633@tekcrl.TEK.COM>
Date: 13 May 88 17:25:44 GMT
References: <2855@phoenix.Princeton.EDU+
Reply-To: terryl@tekcrl.tek.com
Distribution: na
Organization: Tektronix, Inc., Beaverton,  OR.
Lines: 46


In article <2855@phoenix.Princeton.EDU+ lgy@pupthy2.PRINCETON.EDU (Larry Yaffe) writes:
+
+    Are there any versions of cpp which allow one to define macros which
+accept variable numbers of arguments?  I keep wishing for this every time
+I try to move code developed using sysV sprintf to a BSD system, so that
+I could do something like:
+
+#ifdef	BSD_TO_5_SPRINTF
+char	*(*Sprintf)() = sprintf ;
+#define sprintf(...)		strlen (Sprintf (...))
+#endif
+
+#ifdef	5_TO_BSD_SPRINTF
+int	(*Sprintf)() = sprintf ;
+#define sprintf(str,...)	((void) Sprintf (str,...), str)
+#endif

     I came across this kludge years ago, hope it helps:
#define	sprintf(prf)	{ Sprintf prf }

     The TRICK is to ADD an extra level of parentheses, using it like thus:

		sprintf( (buffer,"<what-ever-string-you-want>",<varargs>) );

This makes cpp THINK there is only one argument to the macro; I know you
don't want to muck with the sources and just want to put in the #define
and be done with it, but this is the only way I know of.

+    I know that some systems have `vsprintf' or some such thing which
+can be called from a sprintf replacement routine, but since the vprintf
+routines are not universally available (sadly), using them seems only
+to add to portability problems.
+
+    Does anyone know why the folks at Berkeley chose to have their
+sprintf return its first argument, instead of the number of characters
+printed?  I can't think of any good reason for this choice, since it
+throws away valuable information (the # of characters printed) which
+is painful to reacquire.

     How painful is a strlen???? (I.E. I really don't understand your
complaint). Since Berkeley code is almost always derived upon ATT (or
whatever they're calling themselves this year!!! (-:) code, it sounds
like an earlier version of sprintf returned its first argument. However,
I also can't really think of any good reason for one return value over
the other.......