template in error

[eiji]

Hi folks,

I have a linker - problem using a Matrix-template.
Maybe someone can help me with that.

Q:
"using femath::Matrix" or "using femath::Matrix< double>";

Consider this:

############### ###########
namespace femath {
....
template<class T> class Matrix
{
public:
Matrix();
Matrix(int rows);
Matrix(int rows, int columns);
virtual ~Matrix();
....
};
} //end namespace

namespace fesolv {

using femath::Matrix;

class AbstractSolver
{
public:
AbstractSolver( Model* model);
virtual ~AbstractSolver ();

public:
virtual void Solve()=0;
....
protected:
Model* _model;
Matrix<double>* _systemstiffnes smatrix;
....
};

} //end namespace

############### ###########

Everything compiles great but the linker tells me:
AbstractSolver. obj : error LNK2019: unresolved external symbol "public:
__thiscall femath::Matrix< double>::Matrix <double>(int) "
(??0?$Matrix@N@ femath@@QAE@H@Z ) referenced in function "public:
__thiscall fesolv::Abstrac tSolver::Abstra ctSolver(class fesolv::Model
*)" (??0AbstractSol ver@fesolv@@QAE @PAVModel@1@@Z)
......

I'm using VC++2005 and there is no external *.lib.
Matrix<class T> is in the same compile/link-unit.

Thanks a lot,
Sascha

[Stephan Brönnimann]

eiji wrote:

Hi folks,

I have a linker - problem using a Matrix-template.
Maybe someone can help me with that.

Q:
"using femath::Matrix" or "using femath::Matrix< double>";
using femath::Matrix;

Consider this:

############### ###########
namespace femath {
...
template<class T> class Matrix
{
public:
Matrix();
Matrix(int rows);
Matrix(int rows, int columns);
virtual ~Matrix();
...
};
} //end namespace

namespace fesolv {

using femath::Matrix;

class AbstractSolver
{
public:
AbstractSolver( Model* model);
virtual ~AbstractSolver ();

public:
virtual void Solve()=0;
...
protected:
Model* _model;
Matrix<double>* _systemstiffnes smatrix;
...
};

} //end namespace

############### ###########

Everything compiles great but the linker tells me:
AbstractSolver. obj : error LNK2019: unresolved external symbol "public:
__thiscall femath::Matrix< double>::Matrix <double>(int) "
The constructor
template<typena me T> Matrix<T>::Matr ix(int);
is not implemented ...
(??0?$Matrix@N@ femath@@QAE@H@Z ) referenced in function "public:
__thiscall fesolv::Abstrac tSolver::Abstra ctSolver(class fesolv::Model
*)" (??0AbstractSol ver@fesolv@@QAE @PAVModel@1@@Z)

.... and it is called from the constructor of fesolv::Abstrac tSolver.

Regards, Stephan

[eiji]

That is clear. The constructor is called but not found. So why?
template<class T> Matrix<T>::Matr ix(int)
{
...
}
exists!

Is there a "template<T >" phrase missing?
What can be the problem?

[TB]

eiji sade:

That is clear. The constructor is called but not found. So why?
template<class T> Matrix<T>::Matr ix(int)
{
...
}
exists!

But where?
Is there a "template<T >" phrase missing?
What can be the problem?

TB

[eiji]

I tried this:

//main.cpp
namespace test {

template<class T> class Test
{
T i;
public:
Test(T t);

};

template<class T> Test<T>::Test(T t)
{
i = t;
}

}
int main(int argc , char *argv[])
{
using namespace test;
Test<int> T(1);
return 0;
}
#######

Compiles and links without problems!

but handling it this way:
#######
//a.h
namespace test {

template<class T> class Test
{
T i;
public:
Test(T t);

};
}
#####
//a.cpp
#include "a.h"
namespace test {

template<class T> Test<T>::Test(T t)
{
i = t;
}

}
//main.cpp
#include "a.h"
int main(int argc , char *argv[])
{
using namespace test;
Test<int> T(1);
return 0;
}

same error, the constructor is not found!
Any important linker-options?

Sorry, any suggestions?
Sascha

[TB]

eiji sade:

I tried this: <snip> but handling it this way:
#######
//a.h
namespace test {

template<class T> class Test
{
T i;
public:
Test(T t);

};
}
#####
//a.cpp
#include "a.h"
namespace test {

template<class T> Test<T>::Test(T t)
{
i = t;
}

} <snip>
same error, the constructor is not found!
Any important linker-options?

Sorry, any suggestions?
Sascha

Compiler limitations. The template declarations and definitions must
be in the same translation unit.

Other solutions:
* Read about support for the 'export'-keyword for you compiler.
* #include the cpp-file after the declarations in the header-file.

TB

[Ben Pope]

eiji wrote:

Hi folks,

I have a linker - problem using a Matrix-template.
Maybe someone can help me with that.

class Model;

namespace femath {
template<class T> class Matrix
{
public:
Matrix();
Matrix(int rows);
Matrix(int rows, int columns);
virtual ~Matrix();
};
} //end namespace

namespace fesolv {

using femath::Matrix;

class AbstractSolver
{
public:
AbstractSolver( Model* model);
virtual ~AbstractSolver ();

public:
virtual void Solve()=0;
protected:
Model* model_;
Matrix<double>* systemstiffness matrix_;
};
}

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

Works for me.

Ben Pope
--
I'm not just a number. To many, I'm known as a string...

[eiji]

TB schrieb:

Compiler limitations. The template declarations and definitions must
be in the same translation unit.

Other solutions:
* Read about support for the 'export'-keyword for you compiler.
* #include the cpp-file after the declarations in the header-file.

TB

Most of the linker errors I have solved with that(declaratio n and
definition in the same translation unit). One more to go(link
operator). This is nearly the same problem.

Please Consider this:
############### ######
namespace femath {

template<class T> class Matrix
{
public:
Matrix();
...
friend std::valarray<T > operator*(const Matrix& A, const
std::valarray<T >& b);
...
};
....
template<class T> std::valarray<T > operator*(const Matrix<T>& A, const
std::valarray<T >& b)
{
...
}
};

typedef std::valarray<d ouble> DoubleVector;

void LinearSolver::C omputeSystemRea ctionVector()
{

Matrix<double>* tempStiffness = new Matrix<double>;
...
DoubleVector* uglob = new DoubleVector(0. 0,dimension);
...
(*_reactionforc e) = (*tempStiffness )*(*uglob);

delete uglob;
delete tempStiffness;
}
############### ######
Error message:
LinearSolver.ob j : error LNK2019: unresolved external symbol "class
std::valarray<d ouble> __cdecl femath::operato r*(class
femath::Matrix< double> const &,class std::valarray<d ouble> const &)"
(??Dfemath@@YA? AV?$valarray@N@ std@@ABV?$Matri x@N@0@ABV12@@Z) referenced
in function "private: void __thiscall
fesolv::LinearS olver::ComputeS ystemReactionVe ctor(void)"
(?ComputeSystem ReactionVector@ LinearSolver@fe solv@@AAEXXZ)
############### ######

The code works fine before translating Matrix into a template. The
operator works as expected.
Now the operator is not found during linkage. There must be one reason
why the definition is not accepted, but the declaration does.

Regards,
Sascha

[Ben Pope]

eiji wrote:

I tried this:

//main.cpp
namespace test {

template<class T> class Test
{
T i;
public:
Test(T t);

};

template<class T> Test<T>::Test(T t)
{
i = t;
}

}
int main(int argc , char *argv[])
{
using namespace test;
Test<int> T(1);
return 0;
}
#######

Compiles and links without problems!

but handling it this way:
#######
//a.h
namespace test {

template<class T> class Test
{
T i;
public:
Test(T t);

};
}
#####
//a.cpp
#include "a.h"
namespace test {

template<class T> Test<T>::Test(T t)
{
i = t;
}

}
//main.cpp
#include "a.h"
int main(int argc , char *argv[])
{
using namespace test;
Test<int> T(1);
return 0;
}

same error, the constructor is not found!
Any important linker-options?

Test is a template, so the compiler must be able to see the definition.

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

Ben Pope
--
I'm not just a number. To many, I'm known as a string...

[eiji]

> Test is a template, so the compiler must be able to see the definition.

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

Ben Pope

Thanks Ben, great link!
############### #
//pre-declare each template friend function, add <> in the friend
lines
template<class T> class Matrix;
template<class T> std::valarray<T > operator* (const Matrix<T>& A, const
std::valarray<T >& b);
template<class T> Matrix<T> operator*(const Matrix<T>& A, const
Matrix<T>& B);

template<class T> class Matrix
{
public:
...
friend std::valarray<T > operator* <> (const Matrix& A, const
std::valarray<T >& b);
friend Matrix operator* <> (const Matrix& A, const Matrix& B);
...
};
############### #

Works fine!
Thank you all for a lesson on template-programming :-)