template definition MUST go in the header file???

[jmborr]

Hi all,

I have a "template.h" file with a class template declaration, and I have "template.cpp" file with the definition of this class template.

It turns out that I have the following compilation error:
undefined reference to `vec<double>::foo()'
After googling, I found a post assuring that the class template definition MUST go along in the header file. They cannot reside in two separate files

Is this for real??

Below are the two files:
//===============template.h=================
template<class T>
class vec{

public:
vec( ){ dim = 0; }
void foo(void);
protected:
int dim ;
};
//===============template.cpp================
#include<iostream.h>
using namespace std;
#include &quot;template.h&quot;

template<class T>
void vec<T>::foo(void){
cout <<&quot;foo function\n&quot;;
}
//===========================================

 

[chipperMDW]

Yes.

Read the FAQ in the C++: UNIX forum.

 

[chipperMDW]

The link to that FAQ:

http://www.tek-tips.com/faqs.cfm?spid=208&sfid=2798

 

[jmborr]

If this is the case, then I'm in trouble because I generate multiple definitions of &quot;foo&quot; !

If I include &quot;template.h&quot; into files &quot;one.cpp&quot; and &quot;two.cpp&quot;, and then I do &quot;g++ one.o two.o&quot;, I will generate two definitions of &quot;foo&quot; function.

Any standar get-around this??

jose,

 

[chipperMDW]

I don't see the problem.

It worked fine for me.

Try it and post the errors you get.