Path: utzoo!attcan!uunet!mcvax!ukc!warwick!geoff
From: geoff@cs.warwick.ac.uk (Geoff Rimmer)
Newsgroups: comp.lang.c
Subject: Re: Recursive #includes
Message-ID: <1567@ubu.warwick.UUCP>
Date: 11 Mar 89 17:11:29 GMT
References: <570@marob.MASA.COM> <9727@smoke.BRL.MIL> <964@philmds.UUCP> <3804@xyzzy.UUCP> <7488@june.cs.washington.edu> <9804@smoke.BRL.MIL>
Sender: news@warwick.UUCP
Organization: Computer Science, Warwick University, UK
Lines: 61
In-reply-to: gwyn@smoke.BRL.MIL's message of 6 Mar 89 16:28:10 GMT

In article <9804@smoke.BRL.MIL> gwyn@smoke.BRL.MIL (Doug Gwyn ) writes:
> In article <7488@june.cs.washington.edu> ka@june.cs.washington.edu (Kenneth Almquist) writes:
> >I've been told that incomplete types cannot be used in function prototypes.
> 
> I couldn't find such a prohibition in the pANS.
> (But maybe it's there and I missed it.)

gcc will not allow it:

Script started on Sat Mar 11 17:04:06 1989
--geoff@emerald%   cat str.c

static void function (struct egg * a);

struct egg { int number1; float number2; };

static void function (struct egg * a)
{
        printf("In function with [%d,%f]\n",a->number1,a->number2);
}

extern void main (void)
{
        struct egg aa;
        aa.number1=23;
        aa.number2=12.345;
        function(&aa);
}

--geoff@emerald%   gcc -v
gcc version 1.34
--geoff@emerald%   gcc -ansi -pedantic str.c
str.c:1: warning: `struct egg' declared inside parameter list
str.c: In function function:
str.c:6: conflicting types for `function'
str.c:1: previous declaration of `function'
--geoff@emerald%   exit

script done on Sat Mar 11 17:05:06 1989

The strange thing is that it doesn't barf on the 

	struct void function (struct egg *a);

line, even though the structure is as yet undefined.  The problem is
when it compares the types of the function's arguments, and sees that
in the call to the function, the argument is type (struct egg *) and
in the declaration it is unknown.

Is this a problem with gcc, or does this happen with all ANSI compilers?

Geoff

	------------------------------------------------------------
	Geoff Rimmer, Computer Science, Warwick University, England.
			geoff@uk.ac.warwick.emerald

		"Ahhh, bonjour, monsieur."
		"Sod off."
			- Blackadder 3.
	------------------------------------------------------------