Path: utzoo!attcan!telly!lethe!yunexus!ists!helios.physics.utoronto.ca!news-server.csri.toronto.edu!bonnie.concordia.ca!uunet!zaphod.mps.ohio-state.edu!rpi!batcomputer!munnari.oz.au!manuel!csc.canberra.edu.au!echo!eyal
From: eyal@echo.canberra.edu.au (Eyal Lebedinsky)
Newsgroups: comp.std.c
Subject: 3.7.2 External Object Definitions
Summary: how to define mutualy referencing static structs.
Keywords: external,linkage,declaration,definition
Message-ID: <eyal.665840220@echo>
Date: 6 Feb 91 11:37:00 GMT
Sender: news@csc.canberra.edu.au
Organization: Info Sci & Eng, University of Canberra
Lines: 37


G'day

I have a situation where two static structures at the external level
are defined and initialized to each have a member pointer to the other.
My problem is finding the proper ANSI declarations/definitions for this
case.

It is obvious that the second object defined should first have a
forward declaration for the first object to be properly initialized.
Maybe a sketch will do here:

	<linkage> struct x i7;
	static struct x i6 = { &i7 };
	<linkage> struct x i7 = { &i6 };

Now, the <linkage> is what I find different compilers have different
expectations of. ANSI 3.7.2 is where I looked for the answer. I tried
gnu (1.39) which I hope is ANSI by now. It likes this one:

(1)	extern int i7;
(2)	static int i7 = 1;

It hates this one:

	static int i7;		/* tentative definition, internal linkage */
(3)	extern int i7 = 1;

Microsoft 5.1 likes both, but I wouldn't trust it much.

Q: what should the comment on the right say for (1,2,3) in the sense on
the examples at the end of 3.7.2? What I want is to first give a
'tentative definition' or a 'declaration' followed later by the
initialized 'definition'.

I know how shady this area is with traditional compilers and do not wish to
discuss it, so please limit replies to ANSI issues.