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Date: Sat, 28 Jul 2007 08:04:31 -0700
From: Brian Dessent <brian AT dessent DOT net>
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Subject: Re: Creating dll in cygwin gives "Undefined reference" errors
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Pradip Jadav wrote:

> But when I compiles in cygwin it gives me some "Undefined reference" errors.
> Take an example,
> 
>  /cygdrive/e/DOCUME~1/LOCALS~1/Temp/ccLMFYUe.o:sample.c:(.text+0x4c):
> undefined reference to `createlog(int, char*, ...)'
> 
> Now this "createlog" function is defined in one of .cpp file of my
> main program.(Just for your information)
> 
> Can you help me to solve problem of "undefined reference" ??

The undefined reference is because fundamentally ELF (Linux) and PE/COFF
(Windows) are very different in terms of how linking works under the
hood.  The short explanation is that PE/COFF requires all references to
be resolved at link-time, thus you have to explicitly tell the linker
where createlog() is to be found.

But I've typed this explanation so many times, I think I'll just start
linking to past copies of it:

http://www.cygwin.com/ml/cygwin/2005-07/msg00675.html
http://www.cygwin.com/ml/cygwin/2006-12/msg00592.html
http://www.cygwin.com/ml/cygwin/2007-06/msg00450.html

Brian

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