Path: utzoo!utgpu!news-server.csri.toronto.edu!rutgers!usc!samsung!uunet!lupine!rfg
From: rfg@NCD.COM (Ron Guilmette)
Newsgroups: comp.std.c
Subject: Re: prototypes required ?
Keywords: printf stdargs prototypes
Message-ID: <2150@lupine.NCD.COM>
Date: 19 Oct 90 01:25:00 GMT
References: <4026@otis.oakhill.UUCP> <14164@smoke.BRL.MIL>
Organization: Network Computing Devices, Inc., Mt. View, CA
Lines: 58

In article <14164@smoke.BRL.MIL> gwyn@smoke.BRL.MIL (Doug Gwyn) writes:
>In article <4026@otis.oakhill.UUCP> jeff@oakhill.UUCP (Jeff Enderwick) writes:
>>Is it legal for a compilation system to require prototypes when stdarg
>>functions are used ? It valid for the compiler to require you to include
>>the prototype:
>>	int printf ( const char*, ... );
>>before making the call:
>>	 printf ( "hello %d worlds\n", 5 );
>
>Yes, you definitely must have a prototype in scope before calling a
>variable-argument function in a strictly conforming program.
>
>For printf(), you should #include <stdio.h> instead of declaring it
>yourself.  You might get better results that way in some implementations.

Along the same lines, I also have a related question.

Now please excuse my almost total ignorance regarding the x3j11 requirements
regarding the contents of include files, but I don't immediately see where
(in 4.9.1) it says (explicitly) what function are required to be declared
within <stdio.h>.  Are all of the function listed in 4.9.4 thru 4.9.10
required to have declarations within <stdio.h>?  If so, are they required
to have prototyped declarations?  Non-prototyped?  Either?

Part of the reason that I ask is that I was doing some work recently on
a machine for which the va_list type is a structure, and I encountered
an odd problem.

I was porting some code to this machine, and I got an error on a hunk of
code like:

	#include <stdio.h>
	...
	...
	va_list args;
	...
	vfprintf (file, fmt, args);	/* <= error here */

as it turned out, the creators of the <stdio.h> file in question had cheated
and put a declaration like the following in it:

	int vfprintf (FILE *, const char *, void *);

Obviously, that last formal parameter type is not correct!  That's why I
got an error at the call.

I tried changing the last formal type to (a more correct) `va_list', but
when I did that this changed the <stdio.h> file into something that could
*not* be included ALL BY ITSELF into *any* given file.  Rather, it now always
had to be preceeded by a #include <stdarg.h>.

So what it the `correct' thing to have in the <stdio.h> file regarding the
vfprintf function (and friends)?
-- 

// Ron Guilmette  -  C++ Entomologist
// Internet: rfg@ncd.com      uucp: ...uunet!lupine!rfg
// Motto:  If it sticks, force it.  If it breaks, it needed replacing anyway.