Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP
Path: utzoo!watmath!clyde!caip!topaz!nike!ucbcad!ucbvax!decvax!decwrl!glacier!mips!hansen
From: hansen@mips.UUCP
Newsgroups: net.lang.c
Subject: Re: variable # of args portability?
Message-ID: <551@mips.UUCP>
Date: Tue, 8-Jul-86 23:15:57 EDT
Article-I.D.: mips.551
Posted: Tue Jul  8 23:15:57 1986
Date-Received: Thu, 10-Jul-86 01:21:47 EDT
References: <809@ucbcad.BERKELEY.EDU>
Organization: MIPS Computer Systems, Sunnyvale, CA
Lines: 27

> I want to be able to write a function that will take an unknown number
> of arguments and then call another such function with these arguments,
> namely something like printf() that calls _doprnt() without processing
> its arguments at all.  I know there is no way to write this code portably,
> but is it reasonable to assume that I will be able to do it at all in
> most common implementations of C?  Also, how safe is it to assume that there
> will be something like _doprnt() available?  I know it's not good to depend on
> things like this, but I don't want to have to write my own printf()...
> 
> 	Wayne

System V defines functions named vprintf, vfprintf, and vsprintf,
that combined with the macros defined in varargs.h, provide a
reasonably portable interface to _doprnt.  The first two
functions are trivial to implement on a machine that has _doprnt,
the third is a little tricker, since you must trick the stdio package
into outputting into a string, and the necessary flag setting
is rather unportable (which is why the v...printf functions should
be defined in the system-provided library).

Using varargs.h goes a long way toward making such functions portable.

-- 

Craig Hansen			|	 "Evahthun' tastes
MIPS Computer Systems		|	 bettah when it
...decwrl!mips!hansen		|	 sits on a RISC"