template, undefined reference to fnc

[Lodhart]

Hi, i have a problem with compiling these file:

/** @file struct.h */
 
#ifndef STRUCT_H
#define STRUCT_H
 
using namespace std;
 
...
 
template <typename cStruct> int InitLine(cStruct * toStruct);
template <typename cStruct, typename cItem> int AddToLine(cStruct * toStruct, cItem * newItem);
template <typename cStruct, typename cItem> int DeleteFromLine(cStruct * toStruct, cItem * delItem);
 
#endif // STRUCT_H

/** @file struct.h */

#ifndef STRUCT_H
#define STRUCT_H

using namespace std;

...

template <typename cStruct> int InitLine(cStruct * toStruct);
template <typename cStruct, typename cItem> int AddToLine(cStruct * toStruct, cItem * newItem);
template <typename cStruct, typename cItem> int DeleteFromLine(cStruct * toStruct, cItem * delItem);

#endif // STRUCT_H

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/** @file struct.cpp */
 
#include "struct.h"
 
template <typename cStruct> int InitLine(cStruct * toStruct)
{
  toStruct->first=NULL;
  toStruct->last=NULL;
  toStruct->top=0;
 
  return 0;
}
...

/** @file struct.cpp */

#include "struct.h"

template <typename cStruct> int InitLine(cStruct * toStruct)
{
  toStruct->first=NULL;
  toStruct->last=NULL;
  toStruct->top=0;

  return 0;
}
...

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/** @file mainwindow.h */
 
#ifndef MAINWINDOW_H
#define MAINWINDOW_H
 
#include "struct.h"
 
...
 
#endif // MAINWINDOW_H

/** @file mainwindow.h */

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include "struct.h"

...

#endif // MAINWINDOW_H

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and when i call fnc from mainwindow.cpp

InitLine(NewLine);

InitLine(NewLine);

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the compile output is:
.../mainwindow.cpp:702: undefined reference to `int InitLine<TMyStruct>(TMyStruct*)'

[rknowles]

A template implementation must be visible at compile time. The code you show as "struct.cpp" should be part of "struct.h", not in its own file. Then when "mainwindow" is compiled, the template will be found.