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From: arnold@emory.uucp (Arnold D. Robbins {EUCC})
Newsgroups: comp.lang.c
Subject: Question on external struct declarations in ANSI C
Message-ID: <2189@emory.uucp>
Date: Mon, 3-Aug-87 14:42:43 EDT
Article-I.D.: emory.2189
Posted: Mon Aug  3 14:42:43 1987
Date-Received: Tue, 4-Aug-87 04:17:41 EDT
Organization: Math & Computer Science, Emory University, Atlanta
Lines: 29
Keywords: extern, struct, ansi, gnu cc

I recently put up the latest version of GNU CC (1.7) on my vaxen. Noticing
that it produced really nice code, I decided that, *for fun*, I would try
recompiling my kernel with it. (Let's NOT restart the whole "optimize my
kernel" discussion; that's not what I am interested in.)

Well, the kernel header files are full of declarations like

	extern struct pte Mbmap[];		/* page tables to map mbutl */

where, e.g., what a 'struct pte' is has not been previously defined. /bin/cc
lets you do this, and does not complain until you try to actually use one of
these things or a member of one. GNU CC, on the other hand, promptly dies
miserably when it sees such a declaration. GNU CC claims to follow the rules
of (a version of) the draft standard.

My question is, "is such a declaration illegal?". If so, could someone cite
chapter and verse in the current ANSI draft standard? If such a declaration,
*without* any subsequent use, is illegal, then an awful lot of existing
code is going to break.

On the other hand, if GNU CC is broken, then the GNU people need to be
told about it.

Thanks,
-- 
Arnold Robbins
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