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From: chris@mimsy.UUCP (Chris Torek)
Newsgroups: comp.lang.c
Subject: Re: using varargs function to call another varargs function
Message-ID: <7268@mimsy.UUCP>
Date: Tue, 30-Jun-87 18:45:55 EDT
Article-I.D.: mimsy.7268
Posted: Tue Jun 30 18:45:55 1987
Date-Received: Wed, 1-Jul-87 06:52:05 EDT
References: <1332@rosevax.Rosemount.COM>
Organization: U of Maryland, Dept. of Computer Science, Coll. Pk., MD 20742
Lines: 62

In article <1332@rosevax.Rosemount.COM> dave@rosesun.Rosemount.COM
(Dave Marquardt) writes:
>#include <curses.h>
>
>WINDOW	*window1;
>
>dprintf(a,b,s,va_alist)
>int	a,b;
>char	*s;
>va_dcl
>{
>	wmove(window1, a, b);
>	wprintw(window1, s, va_alist);
>}
>
>First off, can you do something like this?

No.

>Secondly, I doubt that I have the syntax right.

That is close enough.

There are two problems.  First, varargs is (as far as I can tell)
only `kosher' when used for all the arguments.  (The dpANS stdarg
variable-argument-list mechanism works differently, and so I consider
this a minor violation.  Declaring a few fixed arguments seems to
work in all the implementations I have used.)  More important,
though, is that wprintw takes a variable argument list, not a
single argument of type `va_list'.

System V has some of what you need in the form of `vprintf'.  If
curses had a wvprintw, you could do this:

	#include <curses.h>
	#include <varargs.h>

	WINDOW *window1;
	dprintf(va_alist)
		va_dcl
	{
		int a, b;
		char *fmt;
		va_list l;

		va_start(l);
		a = va_arg(l, int);
		b = va_arg(l, int);
		fmt = va_arg(l, char *);
		wmove(window1, a, b);
		wvprintw(window1, fmt, l);
	}

`vprintf' takes a format and an argument of type `va_list'.  vfprintf
takes one additional file pointer, and vsprintf takes a string
pointer.  All return the number of characters printed.  This is
clearly the Right Way to allow this sort of thing; indeed, it
suggests that printf, fprintf, and sprintf themselves be implemented
using <varargs.h> (or <stdarg.h>), and hence portable.
-- 
In-Real-Life: Chris Torek, Univ of MD Comp Sci Dept (+1 301 454 7690)
Domain:	chris@mimsy.umd.edu	Path:	seismo!mimsy!chris