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Oct 22nd, 2008
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Templated Class Compile Error

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I have three files (myClass.h, myClass.cpp, and main.cpp)

C++ Syntax (Toggle Plain Text)
  1. //
  2. // myClass.h
  3.  
  4. #ifndef MYCLASS_H_
  5. #define MYCLASS_H_
  6.  
  7. template <class element_type>
  8. class myClass
  9. {
  10. public:
  11. 	myClass();
  12.  
  13. 	~myClass();
  14. };
  15.  
  16. #endif /* MYCLASS_H_ */

C++ Syntax (Toggle Plain Text)
  1. //
  2. // myClass.cpp
  3.  
  4. #include "myClass.h"
  5.  
  6. template <class element_type>
  7. myClass<element_type>::myClass()
  8. {
  9.  
  10. }
  11.  
  12.  
  13. template <class element_type>
  14. myClass<element_type>::~myClass()
  15. {
  16.  
  17. }

C++ Syntax (Toggle Plain Text)
  1. //
  2. // main.cpp
  3.  
  4.  
  5. #include "myClass.h"
  6.  
  7. int main()
  8. {
  9. 	myClass<int> classOBJ;
  10.  
  11.  
  12. 	return 0;
  13. }


I tried compiling this in VC++ Express, Dev-Cpp, and Eclipse

All give me roughly the same error. From eclipse

Quote originally posted by errors ...
undefined reference to `myClass<int>::~myClass()' main.cpp heapProj 15 C/C++ Problem
undefined reference to `myClass<int>::myClass()' main.cpp heapProj 12 C/C++ Problem
This leads me to believe that I'm coding something wrong, but I just can't track it down for some reason. What's the problem?
Last edited by chococrack; Oct 22nd, 2008 at 12:09 pm.
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Oct 22nd, 2008
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Re: Templated Class Compile Error

I am not sure, but i think you should try including

iostream too.
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Oct 22nd, 2008
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Re: Templated Class Compile Error

Click to Expand / Collapse  Quote originally posted by Sky Diploma ...
try including iostream too.
No change.
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Oct 22nd, 2008
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Re: Templated Class Compile Error

Quote ...
i think you should try including
iostream too.
No need, theres no references to anything in iostream yet.
Last edited by William Hemsworth; Oct 22nd, 2008 at 12:18 pm.
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Oct 22nd, 2008
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Re: Templated Class Compile Error

Alas, it's impossible now to separate template class declaration and implementation. Why? Have a look at
http://www.parashift.com/c++-faq-lit...html#faq-35.12
So place all your cpp file contents into template definition header file (then wait for a new compilers generation )...
Last edited by ArkM; Oct 22nd, 2008 at 12:28 pm.
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Oct 22nd, 2008
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Re: Templated Class Compile Error

That's got to be it, because I do know that if I stack them all together in one file, everything runs without a problem.

The only compiler I know of that actually allows this separation so far (in my studies) is the Sun Studio 12 "CC" compiler

That link is golden.
Last edited by chococrack; Oct 22nd, 2008 at 12:47 pm.
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Oct 22nd, 2008
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Re: Templated Class Compile Error

SOLUTION:
TWO files: myClass.h main.cpp

C++ Syntax (Toggle Plain Text)
  1. //
  2. // myClass.h
  3.  
  4. #ifndef MYCLASS_H_
  5. #define MYCLASS_H_
  6.  
  7. template <class element_type>
  8. class myClass
  9. {
  10. public:
  11. 	myClass();
  12.  
  13. 	~myClass();
  14. };
  15.  
  16. template <class element_type>
  17. myClass<element_type>::myClass()
  18. {
  19.  
  20. }
  21.  
  22.  
  23. template <class element_type>
  24. myClass<element_type>::~myClass()
  25. {
  26.  
  27. }
  28.  
  29. #endif /* MYCLASS_H_ */

C++ Syntax (Toggle Plain Text)
  1. //
  2. // main.cpp
  3.  
  4.  
  5. #include "myClass.h"
  6.  
  7. int main()
  8. {
  9. 	myClass<int> classOBJ;
  10.  
  11.  
  12. 	return 0;
  13. }
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Oct 22nd, 2008
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Re: Templated Class Compile Error

Click to Expand / Collapse  Quote originally posted by chococrack ...
SOLUTION:
TWO files: myClass.h main.cpp

C++ Syntax (Toggle Plain Text)
  1. //
  2. // myClass.h
  3.  
  4. #ifndef MYCLASS_H_
  5. #define MYCLASS_H_
  6.  
  7. template <class element_type>
  8. class myClass
  9. {
  10. public:
  11. 	myClass();
  12.  
  13. 	~myClass();
  14. };
  15.  
  16. template <class element_type>
  17. myClass<element_type>::myClass()
  18. {
  19.  
  20. }
  21.  
  22.  
  23. template <class element_type>
  24. myClass<element_type>::~myClass()
  25. {
  26.  
  27. }
  28.  
  29. #endif /* MYCLASS_H_ */

C++ Syntax (Toggle Plain Text)
  1. //
  2. // main.cpp
  3.  
  4.  
  5. #include "myClass.h"
  6.  
  7. int main()
  8. {
  9. 	myClass<int> classOBJ;
  10.  
  11.  
  12. 	return 0;
  13. }
That's one way of doing it, but you could also use eager-inclusion.

c++ Syntax (Toggle Plain Text)
  1.  
  2. // file.h
  3. #ifndef MYHEADER_H
  4. #define MYHEADER_H
  5.  
  6. /*Declaractions*/
  7. #include "file.cpp"
  8.  
  9. #endif

c++ Syntax (Toggle Plain Text)
  1.  
  2. // file.cpp
  3. #ifdef MYHEADER_H
  4.  
  5.  
  6. #endif

c++ Syntax (Toggle Plain Text)
  1.  
  2. #include "file.h"
  3.  
  4. int main(){
  5.  
  6.    return 0;
  7. }

And also instead of eager inclusion you can simply add the .cpp file later in the driver file, and include the header file in the driver file.
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