Path: utzoo!mnetor!uunet!husc6!bbn!oberon!skat.usc.edu!blarson
From: blarson@skat.usc.edu (Bob Larson)
Newsgroups: comp.lang.c
Subject: Re: problems with varargs
Message-ID: <6394@oberon.USC.EDU>
Date: 22 Jan 88 07:13:55 GMT
References: <7962@eleazar.Dartmouth.EDU>
Sender: nobody@oberon.USC.EDU
Reply-To: blarson@skat.usc.edu (Bob Larson)
Organization: USC AIS, Los Angeles
Lines: 57
Keywords: varargs

In article <7962@eleazar.Dartmouth.EDU> cmi@eleazar.Dartmouth.EDU (Theo Pozzy/R. Green) writes:
>I'm have a problem working with the standard *nix varargs construct.
>myprintf(fmt, va_alist)
>char *fmt;
>va_dcl
>{
>va_list vap;
>va_start(vap);
>/* here I can pull of the arguments with no problem */
>myfprintf(stdout,fmt,vap);
>va_end(vap);
>}
va_alist MUST be the only argument to a varargs function.  (Lint (sun
3.2) gets this horrably WRONG.  If you don't get a ton of error
messages from lint you made a mistake.  (This is another case where
something non-portable happens to work on 4.2bsd so people assume it
works everywhere.)

myprintf(va_alist)
va_dcl
{
va_list vap;
char *fmt;
va_start(vap);
fmt = va_arg(vap, char *);
myfprintf(stdout, fmt, vap);
va_end(vap);
}

>myfprintf(f, fmt, va_alist)
>FILE *f;
>char *fmt;
>va_dcl
>{
>va_list vap;
>va_start(vap);
>/* at this point, the va_arg() routine doesn't return the arguments correctly */
>va_end(vap)
>}
This is where your major mistakes are.

myfprintf(f, fmt, vap)
FILE *f;
char *fmt;
va_list vap;
{
/* va_arg should work here */
}


Note that you may have to pass a pointer to vap on systems that
va_list is a structure but don't have structure passing.
--
Bob Larson	Arpa: Blarson@Ecla.Usc.Edu	blarson@skat.usc.edu
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