Path: utzoo!mnetor!uunet!husc6!cmcl2!brl-adm!umd5!mimsy!chris
From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: problems with varargs
Message-ID: <10301@mimsy.UUCP>
Date: 22 Jan 88 15:37:31 GMT
References: <7962@eleazar.Dartmouth.EDU>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 43
Keywords: varargs

In article <7962@eleazar.Dartmouth.EDU> cmi@eleazar.Dartmouth.EDU
(Theo Pozzy/R. Green) writes:
>The basic idea is to have a routine like printf(), which calls another
>routine, like fprintf(), passing one argument in addition to the arguments
>passed to it.

The basic trick (if I may phrase it so) is to have only one va_alist
parameter anywhere in the chain.  printf() does not call fprintf();
printf() calls vfprintf():

myprintf(fmt, va_alist)
	char *fmt;
	va_dcl
{
	va_list vap;

	va_start(vap);
	myvfprintf(stdout, fmt, vap);
	va_end(vap);
}

myfprintf(f, fmt, va_alist)
	FILE *f;
	char *fmt;
	va_dcl
{
	va_list vap;

	va_start(vap);
	myvfprintf(f, fmt, vap);
	va_end(vap)
}

myvfprintf(f, fmt, ap)
	FILE *f;
	char *fmt;
	va_list ap;
{
	...
}
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7163)
Domain:	chris@mimsy.umd.edu	Path:	uunet!mimsy!chris