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From: Brian Inglis <Brian DOT Inglis AT SystematicSw DOT Invalid>
Newsgroups: comp.os.msdos.djgpp
Subject: Re: Environment Variables
Organization: Systematic Software
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Date: Wed, 11 Aug 2004 15:57:43 GMT
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To: djgpp AT delorie DOT com
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Reply-To: djgpp AT delorie DOT com

On 11 Aug 2004 11:47:04 +0300 in comp.os.msdos.djgpp, Esa A E Peuha
<esa DOT peuha AT helsinki DOT fi> wrote:

>Brian Inglis <Brian DOT Inglis AT SystematicSw DOT Invalid> writes:
>
>> Looks like you're correct about -Cg not being entirely truthful about
>> globals without leading _. The revised list of non-Standard globals
>> from a dummy program with no #includes compiled with -ansi -pedantic
>> are: 
>> 
>> T _close	close	*
>> D _edata	edata
>> B _end		end
>> B _environ	environ
>> T _etext	etext
>> T _sbrk		sbrk	*
>> 
>> where the routines marked * are Unix compatible routines called by the
>> startup/exit code. Can be worked around, as you indicate below? 
>
>What version of djgpp are you using?  It seems to be older than the
>current CVS, because with it you shouldn't see _etext, _edata and _end
>unless you actually use them in your code.  (close and sbrk are bugs,
>but they may be fixed already.)

djdev 2.03 PL 2

>> Eli Z pointed out that it must be available for POSIX compatible code
>> that requires it, but should not be present for ANSI compiles. 
>> I would be interested in how you can have it defined, if it is
>> declared, but not defined as a global, and have it not be defined if
>> it is already defined? 
>
>The linker can be instructed (by using the PROVIDE construct in the
>linker script) to define symbols only if they are referenced but not
>defined.  That's how _etext, _edata and _end are defined.

That's a useful facility that I didn't know was possible. 

-- 
Thanks. Take care, Brian Inglis 	Calgary, Alberta, Canada

Brian DOT Inglis AT CSi DOT com 	(Brian dot Inglis at SystematicSw dot ab dot ca)
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