From:	Endlisnis <s257m AT unb DOT ca>
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: help - template<class T>
Date:	Sat, 05 Sep 1998 11:50:04 -0300
Organization:	NBTel Internet
Lines:	32
Message-ID:	<35F14F9C.8570B044@unb.ca>
References:	<35f10110 DOT 1073722 AT news DOT telepac DOT pt>
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To:	djgpp AT delorie DOT com
DJ-Gateway:	from newsgroup comp.os.msdos.djgpp

Jorge Bruno S. S. Morgado wrote:
> template<class T>
> class matrix
> {
> gxx -c -o math.o math.cc
> gxx -c -o main.o main.cc
> gxx -o test.exe main.o math.o
> 
> but this simply doesent work, it gives me lots of errors like:
> function <double> determinant(void) in class matrix not defined, and
> things like that.
> I've also noticed that the file math.o is very smal (only 375 bytes),
> and that, if I put the all class in the file math.h, and just include
> it from main.cc, it all goes fine, but this way, every time I make a
> change in another included file, I have to recompile all of it again.
> 
> Also, when I do something like this (using varios pre-compiled files)
> with C (not C++) it works just fine.
> 
> Is this a bug with gxx ?
> Why does this happens ?
	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.
-- 
     (\/) Endlisnis (\/)
          s257m AT unb DOT ca
          Endlisnis AT GeoCities DOT com
          Endlis AT nbnet DOT nb DOT ca

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