From:	Endlisnis <s257m AT unb DOT ca>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: help - template<class T>
Date:	Mon, 07 Sep 1998 19:07:42 -0300
Organization:	NBTel Internet
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Message-ID:	<35F4592E.F6BBC812@unb.ca>
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To:	djgpp AT delorie DOT com
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Fabrice ILPONSE wrote:
> >         I think it has to do with the way templates are handled.  math.o is small
> > because there is (effectively) nothing in it.  Templates are only compiled
> > when a reference to them if found.  No references are found in math.cc.  I
> > don't think the linker will link templated functions that had no instances
> > during compilation.
> 
>         I'm not sure!!
>         You have to put all the class in the header.
>         The functions are  recreated each time you declare a new template
> variable of an inexisting type.
> 
>         eg.
>                 matrix <int> a,b;
>                 matrix <float> c;
> 
>         in fact there'll be 2 differents classes: 1 for int and 1 for float.
>         So as the compiler need to know the body of the functions to rebuild
> them, they must be in the header file.
	And this happens at COMPILE time, not LINK time.  If during COMPILE time,
there are no instances, then you can't link a program with instances. 
Conclusion:  Don't make a template library file.  You can't precompile
templates, they must be compiled in the same module as the declarations.
-- 
     (\/) Endlisnis (\/)
          s257m AT unb DOT ca
          Endlisnis AT GeoCities DOT com
          Endlis AT nbnet DOT nb DOT ca

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