Date: Tue, 7 Feb 1995 10:48:25 +0100 (CET)
From: "Roland Exler" <R DOT Exler AT jk DOT uni-linz DOT ac DOT at>
Sender: k3a0270 AT pop DOT uni-linz DOT ac DOT at
Reply-To: R DOT Exler AT jk DOT uni-linz DOT ac DOT at
To: <djgpp AT sun DOT soe DOT clarkson DOT edu>
Subject: Multiple definition ... using Templates

Hi anybody,

I've an simple-looking error linking from multiple modules each using the
same instance of a template-class. In the example below 'main' and 'sub'
uses class 'store<int>' declared in file 'temp.h', both compile ok.

Linking the files produces the 'multiple definition'-error as you can see
in the appended file 'ERR.LOG' produced by redirecting the output of make.

Can anybody tell me how to correct this error?

Thanks, Roland
+---------------------------------------+---------------------------+
I Roland Exler                          I EMAIL:                    I
I Universitaet Linz                     I R DOT Exler AT jk DOT uni-linz DOT ac DOT at I
I Institut fuer Elektrische Messtechnik I                           I
I Altenbergerstr. 69                    I Phone:                    I
I A-4040 Linz, AUSTRIA                  I + 43 732 2468 9205        I
+---------------------------------------+---------------------------+
************************ File TEMP.H ********************************
#ifndef _TEMP_H
#define _TEMP_H

template <class TYPE>
class store
{
protected:
  TYPE data;
public:
  store(TYPE daten) {data=daten;};
  TYPE read();
};

template <class TYPE>
TYPE store<TYPE>::read()
{ return data; }

#endif

************************ File MAIN.CC ********************************
#include<iostream.h>
#include "temp.h"

void sub();

int main()
{
  store<int> one(1);
  store<int> two(2);
  cout<<"main: "<<one.read()+two.read()<<endl;
  sub();
  return 0;
}

************************ File SUB.CC ********************************
#include<iostream.h>
#include "temp.h"

void sub()
{
  store<int> one(1);
  store<int> two(2);
  cout<<"sub: "<<one.read()+two.read()<<endl;
}

************************ MAKEFILE ********************************
.cc.o:
	gcc -Wall -O2 -m486 -c $<

.o:
	gcc -Wall -O2 -m486 -o $@ $^ -lgpp

main: main.o sub.o

main.o: main.cc temp.h

sub.o: sub.cc temp.h

************************ File ERR.LOG ********************************
gcc -Wall -O2 -m486 -c main.cc
gcc -Wall -O2 -m486 -c sub.cc
gcc -Wall -O2 -m486 -o main main.o sub.o -lgpp
sub.cc(.text+0x64): multiple definition of `store<int>::read(void)'
main.cc(.text+0x70): first defined here
make.exe: *** [main] Error 1