::Queue()", referenced...">
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Undefined symbols for x86_64 architecture

I have this error:

Undefined symbols for architecture x86_64:
  "my::Queue<int>::Queue()", referenced from:
      _main in ccdwI88X.o
ld: symbol(s) not found for architecture x86_64
collect2: ld returned 1 exit status

for this code 'main.cpp':

#include "Queue.hpp"

int main()
{
  my::Queue<int> myqueue;
  return 0;
}

'Queue.hpp':

#ifndef QUEUE_HH__
#define QUEUE_HH__

namespace my
{
  template <typename T>
  class Queue
  {
  public:
    Queue();     
  };
}

#endif

and 'Queue.cpp':

#include "Queue.hpp"

template <typename T>
my::Queue<T>::Queue() 
{
}
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2 answers

The answer is here: fooobar.com/questions/851251 / ... - this is what I think you need.

If I edit the file Queue.cppfor this:

#include "Queue.hpp"

template <typename T>
my::Queue<T>::Queue() 
{

}

template class my::Queue<int>;

.. it compiles fine.

Detailed explanation, please refer to the above address.

+5
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The easiest and safest way to use templates is to always include the definition (implementation) of class functions inside the file .hpp, and not in a separate file .cpp.

: http://www.parashift.com/c++-faq-lite/templates.html#faq-35.12

+1

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