Linker error when dividing source code into multiple files

[yatko]

Hi all;

I have written a class, and it works fine when all the definitions are
in one main.cpp file. But whenever I divide source code in several
files(main.cpp, class.h, class.cpp), it is compiled with no errors,
but linker gives the following error. I could not find what the
problem is.

Thanks

yatko
----
**** Build of configuration Debug for project test ****

make all
Building target: test
Invoking: GCC C++ Linker
g++ -o"test" ./ProducersNConsumers.o ./main.o -lboost_thread-gcc41-
mt-1_34_1
../main.o: In function `main':
/home/oktay/workspace/test/Debug/../main.cpp:135: undefined reference
to `ProducersNConsumers<int>:roducersNConsumers()'
/home/oktay/workspace/test/Debug/../main.cpp:151: undefined reference
to `ProducersNConsumers<int>::~ProducersNConsumers()'
collect2: ld returned 1 exit status
make: *** [test] Error 1
-----

main.cpp
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
#include <boost/thread/thread.hpp>
#include <iostream>

#include "ProducersNConsumers.h"


boost::mutex io_mutex;
const int BUFFER_SIZE = 1024;
const int ITERS = 100;

volatile bool start = false;



int
main()
{
ProducersNConsumers<int> outgoing;



return 0;
}
--------------------------------------------------------------------------------------------------------------------------------------------------------------------



ProducersNConsumers.h
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
#ifndef PRODUCERSNCONSUMERS_H_
#define PRODUCERSNCONSUMERS_H_

#include <boost/thread/mutex.hpp>
#include <boost/thread/condition.hpp>
#include <list>

extern boost::mutex io_mutex;
extern const int BUFFER_SIZE;
extern const int ITERS;

template <class DataType>
class ProducersNConsumers
{

public:

typedef boost::mutex::scoped_lock scoped_lock;

ProducersNConsumers();

~ProducersNConsumers();

DataType Pop(void);

void Push(DataType);

void Print(void);

private:

struct Node {
DataType data;
bool valid;

Node(DataType, bool);
};

int itemCount;

std::list<Node> buffer;

typename std::list <Node>::iterator popIterator;
typename std::list <Node>::iterator pushIterator;

boost::mutex enter;
boost::condition full;
boost::condition empty;

};


#endif /*PRODUCERSNCONSUMERS_H_*/
--------------------------------------------------------------------------------------------------------------------------------------------------------------------



ProducersNConsumers.cpp
--------------------------------------------------------------------------------------------------------------------------------------------------------------------
#include <iostream>

#include "ProducersNConsumers.h"

template <class DataType>
ProducersNConsumers<DataType>::Node::Node(DataType data = 0, bool
valid = false)
{
}

template <class DataType>
ProducersNConsumers<DataType>:roducersNConsumers()
{
}

template <class DataType>
ProducersNConsumers<DataType>::~ProducersNConsumers()
{

}

template <class DataType>
DataType
ProducersNConsumers<DataType>:op(void)
{

}


template <class DataType>
void
ProducersNConsumers<DataType>:ush(DataType data)
{

}

template<class DataType>
void
ProducersNConsumers<DataType>:rint(void)
{
scoped_lock lock(enter);



}
--------------------------------------------------------------------------------------------------------------------------------------------------------------------

 

[Ian Collins]

Hi all;

I have written a class, and it works fine when all the definitions are
in one main.cpp file. But whenever I divide source code in several
files(main.cpp, class.h, class.cpp), it is compiled with no errors,
but linker gives the following error. I could not find what the
problem is.

gcc doesn't support separation of declarations and definitions of
templates, they have to be included inline.

 

[Keith Halligan]

Hi all;

I have written a class, and it works fine when all the definitions are
in one main.cpp file. But whenever I divide source code in several
files(main.cpp, class.h, class.cpp), it is compiled with no errors,
but linker gives the following error. I could not find what the
problem is.

Thanks

yatko
----
**** Build of configuration Debug for project test ****

make all
Building target: test
Invoking: GCC C++ Linker
g++ -o"test" ./ProducersNConsumers.o ./main.o -lboost_thread-gcc41-
mt-1_34_1
./main.o: In function `main':
/home/oktay/workspace/test/Debug/../main.cpp:135: undefined reference
to `ProducersNConsumers<int>:roducersNConsumers()'
/home/oktay/workspace/test/Debug/../main.cpp:151: undefined reference
to `ProducersNConsumers<int>::~ProducersNConsumers()'
collect2: ld returned 1 exit status
make: *** [test] Error 1

As was already stated gcc/++ does not support separation of templates
between the header and cpp file. Very few compilers actually support
this feature (the only compiler I know of being Comeau).

There are tricks around this, see the entry in the C++ FAQ below:
http://www.parashift.com/c++-faq-lite/templates.html#faq-35.13

 

[yatko]

Thanks guys