Path: utzoo!utgpu!water!watmath!dalcs!garfield!john13
From: john13@garfield.UUCP (John Russell)
Newsgroups: comp.lang.c
Subject: Re: extern
Keywords: extern
Message-ID: <4430@garfield.UUCP>
Date: 23 Jan 88 05:09:25 GMT
References: <17428@topaz.rutgers.edu> <7123@brl-smoke.ARPA> <4405@garfield.UUCP> <7150@brl-smoke.ARPA>
Reply-To: john13@garfield.UUCP (John Russell)
Distribution: na
Organization: Memorial University of Newfoundland, St. John's
Lines: 34

In article <7150@brl-smoke.ARPA> gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>) writes:
>In article <4405@garfield.UUCP> john13@garfield.UUCP (John Russell) writes:
>-file 1 -
>-int fou;

>[I assume "foo" was intended]

Not the point. This exact situation happened to me (with different variable
names of course). DAMN tough to track down! Luckily I noticed the typo
shortly after it occurred (after running the program once).

>-file 2 -
>-extern int foo;
>-foo = 1;
>-then at least some compilers will run this properly (no warnings even).

>PLEASE don't do this.  A compiler is not obliged to make this example
>"work".  

No kidding :-). But I do think it's important to know of this peculiar
behaviour, which could easily cause hard-to-find errors when using "extern".
The original article seemed to be asking *how* extern storage was treated,
and this example shows how the compiler doesn't always behave as you would
assume under an "ideal" model of C.

This was the C on our 4.3BSD system. I was shocked that the linker didn't
complain at all that I was extern'ing a variable, then referring to it, when
it didn't exist in any other module.

John
-- 
"Am I dreaming, or was there a show on this weekend called 'Jimmy the Greek:
 Live at the Apollo'?"
					-- David Letterman