From: fred AT genesis DOT demon DOT co DOT uk (Lawrence Kirby)
Newsgroups: comp.os.msdos.djgpp,comp.lang.c
Subject: Re: Can't get external variables to work!??
Date: Sat, 07 Feb 98 20:02:24 GMT
Organization: none
Message-ID: <886881744snz@genesis.demon.co.uk>
References: <34DC7457 DOT 6A0A7521 AT iafrica DOT com> <slrn6dp2f4 DOT j5q DOT jxh AT lambada DOT cs DOT wustl DOT edu> <34DCAE69 DOT F64D9DCE AT acm DOT org>
Reply-To: fred AT genesis DOT demon DOT co DOT uk
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In article <34DCAE69 DOT F64D9DCE AT acm DOT org> petebecker AT acm DOT org "Pete Becker" writes:

>James Hu wrote:
>> 
>> This problem could have been diagnosed if you had #include'd kbd.h into
>> kbd.c.
>
>Well, no. It's perfectly legal to have an extern declaration followed by
>a static definition.

According to 6.1.2.2 it results in undefined behaviour:

"If, within a translation unit, the same identifier appears with both
 internal and external linkage, the behaviour is undefined."

However as far as I can see no diagnostic is required.

>So the compiler is not required to say anything if
>you do this. I suppose it's possible that some compiler might give you a
>warning because it thinks that you may have made a mistake, but I don't
>know of one that does this.

gcc -pedantic does (so presumably DJGPP does too). The other 2 compilers
I have on this (Unix) platform do too if you put them in ANSI C mode.

-- 
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Lawrence Kirby | fred AT genesis DOT demon DOT co DOT uk
Wilts, England | 70734 DOT 126 AT compuserve DOT com
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