template class member function specialization

[Bjoern Knafla]

Hi!

I am trying to specialize a member function of a template class (see
code below).

The moment the header with the "template class definition" and
"template class member function specialization" is included in two
different translation units (cpp-files).

Problem:
g++ 3.3.3 (or more exact the ld linker 2.14.90.0.7) complains about
multiple definitions / multiple symbols with the same name...

Intels c++ compiler (icc 8.0) compiles the same code without any
problem and links it.


Am I doing something wrong (C++ in a Nutshell shows that code like mine
should work on page 194) or is this a compiler/linker problem?


Kind regards,
Bjoern


Code:
=====

template_class.hpp - contains the specialized template class member
function "type"
------------------------------------------------------------------------------------------------------------------
#ifndef

#ifndef INCLUDED_template_class_HPP
#define INCLUDED_template_class_HPP

template< typename T >
class template_class {
public:
int num() const;
};

template< typename T >
int
template_class<T>::num() const
{
return 0;
}


template<>
int
template_class<float>::num() const
{
return 42;
}


#endif // INCLUDED_template_class_HPP


main.cpp - uses the template class
-----------------------------------------------
#include <iostream>

#include "template_class.hpp"
#include "linker_tester.hpp"

int main (int argc, char * const argv[]) {

(void) argc; // Prevent parameter not used warning.
(void) argv; // Prevent parameter not used warning.

template_class< int > a;
template_class< float > b;

std::cout << "a.num() " << a.num() << std::endl;
std::cout << "b.num() " << b.num() << std::endl;

output();

return 0;
}


linker_tester.hpp - declares a simple function that uses the template class
---------------------------------------------------------------------------------------------------
#ifndef

#ifndef INCLUDED_linker_tester_HPP
#define INCLUDED_linker_tester_HPP

int output();


#endif // INCLUDED_linker_tester_HPP


linker_tester.cpp
----------------------
#include "linker_tester.hpp"

#include <iostream>

#include "template_class.hpp"

int output()
{
template_class< int > a;
template_class< float > b;

std::cout << "output a.num() " << a.num() << std::endl;
std::cout << "output b.num() " << b.num() << std::endl;

return 0;
}

 

[Victor Bazarov]

I am trying to specialize a member function of a template class (see
code below).

The moment the header with the "template class definition" and "template
class member function specialization" is included in two different
translation units (cpp-files).

Problem:
g++ 3.3.3 (or more exact the ld linker 2.14.90.0.7) complains about
multiple definitions / multiple symbols with the same name...

Intels c++ compiler (icc 8.0) compiles the same code without any
problem and links it.


Am I doing something wrong (C++ in a Nutshell shows that code like mine
should work on page 194) or is this a compiler/linker problem?
[...]

It is a compiler/linker problem. I heard bad things about 3.3.3, try
upgrading to 3.4.

V

 

[Bjoern Knafla]

It is a compiler/linker problem. I heard bad things about 3.3.3, try
upgrading to 3.4.

V

Thank you!

Cheers,
Bjoern