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rwm · Sep 5th, 2007, 3:46 AM

Hey!

I had some problems with static template members:

// TClass.hpp
#pragma once

namespace Global
{

namespace A
{

template<typename T>
class TClass
{
    public:
        TClass() {}
        TClass(const T &t) : data(t) {}
        //static member
        static const TClass<T> Default;
    private:
        //data
        T data;
};

//static member declaritions
template<> const TClass<float> TClass<float>::Default(1.0f);
template<> const TClass<double> TClass<double>::Default(1.0);

};

};

As you can see this is nested in two namespaces, Global and A. I've defined a header file:

(Toggle Plain Text)

// Types.hpp
#pragma once

#include "TClass.hpp"

namespace Global
{

namespace A
{

typedef TClass<float> Class;

};

};

Which I use in another class, defined in a different namespace:

(Toggle Plain Text)

//SomeClass.hpp
#pragma once

#include "Types.hpp"
using namespace Global::A;

namespace Global
{

namespace B
{

class SomeClass
{
    //uses Class which is typedef of template<typename T> TClass
};

};

};

I get compiler errors for every static member declared saying that the data was declared more than once? How is that possible?

Hope you can help!

Thanks!

Cache · Sep 5th, 2007, 2:33 PM

Works in VC8 (MSVC 2005) with no errors. Perhaps the 'once' pragma is meaningless in your environment? BTW, C++ doesn't require a semicolon to terminate a namespace.

rwm · Sep 6th, 2007, 2:47 AM

Hey Cache!

Thanks for the reply! Mmm, well that's not exactly the code, but very much along the lines of that...

I've forgotten to bring the source from home, was in such a rush! But it was along the lines of that...

As for semi-colon at end of namespace brace, I do that purposely. I don't know why, I kinda like it... And always add a comment to end as well

(Toggle Plain Text)

namespace blah
{
...
}; //namespace blah

I might have an old backup on my flash disk, i'll have a look, if i find it i'll compile it and post the errror!

rwm · Sep 6th, 2007, 3:00 AM

Found it.

Hey, here's the exact error:

(Toggle Plain Text)

/tmp/cc1uTVHE.o(.bss+0x3d0): multiple definition of `Mathematics::TVector<double>::kZero'
/tmp/ccDuSaWS.o(.bss+0x3d0): first defined here
/tmp/cc1uTVHE.o(.bss+0x3e8): multiple definition of `Mathematics::TVector<double>::kZAxis'
/tmp/ccDuSaWS.o(.bss+0x3e8): first defined here
/tmp/cc1uTVHE.o(.bss+0x400): multiple definition of `Mathematics::TVector<double>::kYAxis'
/tmp/ccDuSaWS.o(.bss+0x400): first defined here
/tmp/cc1uTVHE.o(.bss+0x418): multiple definition of `Mathematics::TVector<double>::kXAxis'
/tmp/ccDuSaWS.o(.bss+0x418): first defined here
/tmp/cc1uTVHE.o(.bss+0x430): multiple definition of `Mathematics::TVector<float>::kZero'
/tmp/ccDuSaWS.o(.bss+0x430): first defined here
/tmp/cc1uTVHE.o(.bss+0x43c): multiple definition of `Mathematics::TVector<float>::kZAxis'
/tmp/ccDuSaWS.o(.bss+0x43c): first defined here
/tmp/cc1uTVHE.o(.bss+0x448): multiple definition of `Mathematics::TVector<float>::kYAxis'
/tmp/ccDuSaWS.o(.bss+0x448): first defined here
/tmp/cc1uTVHE.o(.bss+0x454): multiple definition of `Mathematics::TVector<float>::kXAxis'

From this source:

(Toggle Plain Text)

#pragma once

//local dependencies
#include "Config.hpp"
#include "Types.hpp"

namespace App
{

namespace Mathematics
{

//forward declaritions
template<typename T> class TMath;
template<typename T> class TPoint;

template<typename T>
class ITEM TVector
{
	public:
		//...
		//static members
		ITEM static const TVector<T> kXAxis;
		ITEM static const TVector<T> kYAxis;
		ITEM static const TVector<T> kZAxis;
		ITEM static const TVector<T> kZero;
	private:
		//data
		T vector[3];
	protected:
		//
}; //class TVector

//static member declaritions
//single precision
template<> const TVector<Float> TVector<Float>::kXAxis(1.0f,0.0f,0.0f);
template<> const TVector<Float> TVector<Float>::kYAxis(0.0f,1.0f,0.0f);
template<> const TVector<Float> TVector<Float>::kZAxis(0.0f,0.0f,1.0f);
template<> const TVector<Float> TVector<Float>::kZero(0.0f,0.0f,0.0f);
//double precision
template<> const TVector<Double> TVector<Double>::kXAxis(1.0,0.0,0.0);
template<> const TVector<Double> TVector<Double>::kYAxis(0.0,1.0,0.0);
template<> const TVector<Double> TVector<Double>::kZAxis(0.0,0.0,1.0);
template<> const TVector<Double> TVector<Double>::kZero(0.0,0.0,0.0);

///members go here

}; //namespace Mathematics

}; //namespace App

Is it because i'm declaring static members in the header file?

Hope you can help!

Thanks!

grumpy · Sep 6th, 2007, 7:11 AM

Yes, it is because you're defining the statics in the header file (or, more accuratly, because you're defining them in the header and then including that header in multiple source files [aka non-header files]).

Move the definitions (which are after the comment that says "//static member declaritions" (sic)) so they only appear in a single source file.

rwm · Sep 6th, 2007, 7:40 AM

Hey Grumpy!

Thanks for the reply! Ok, i'll do that!

(Toggle Plain Text)

//static member declaritions

Is this not the right terminology?

Thanks!

rwm · Sep 7th, 2007, 2:09 AM

Well that fixed the problem! Thanks man!

Sep 5th, 2007, 3:46 AM	#1
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	static template members Hey! I had some problems with static template members: (Toggle Plain Text) // TClass.hpp #pragma once namespace Global { namespace A { template<typename T> class TClass { public: TClass() {} TClass(const T &t) : data(t) {} //static member static const TClass<T> Default; private: //data T data; }; //static member declaritions template<> const TClass<float> TClass<float>::Default(1.0f); template<> const TClass<double> TClass<double>::Default(1.0); }; }; // TClass.hpp #pragma once namespace Global { namespace A { template<typename T> class TClass { public: TClass() {} TClass(const T &t) : data(t) {} //static member static const TClass<T> Default; private: //data T data; }; //static member declaritions template<> const TClass<float> TClass<float>::Default(1.0f); template<> const TClass<double> TClass<double>::Default(1.0); }; }; As you can see this is nested in two namespaces, Global and A. I've defined a header file: (Toggle Plain Text) // Types.hpp #pragma once #include "TClass.hpp" namespace Global { namespace A { typedef TClass<float> Class; }; }; // Types.hpp #pragma once #include "TClass.hpp" namespace Global { namespace A { typedef TClass<float> Class; }; }; Which I use in another class, defined in a different namespace: (Toggle Plain Text) //SomeClass.hpp #pragma once #include "Types.hpp" using namespace Global::A; namespace Global { namespace B { class SomeClass { //uses Class which is typedef of template<typename T> TClass }; }; }; //SomeClass.hpp #pragma once #include "Types.hpp" using namespace Global::A; namespace Global { namespace B { class SomeClass { //uses Class which is typedef of template<typename T> TClass }; }; }; I get compiler errors for every static member declared saying that the data was declared more than once? How is that possible? Hope you can help! Thanks!

Sep 6th, 2007, 2:47 AM	#3
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	Hey Cache! Thanks for the reply! Mmm, well that's not exactly the code, but very much along the lines of that... I've forgotten to bring the source from home, was in such a rush! But it was along the lines of that... As for semi-colon at end of namespace brace, I do that purposely. I don't know why, I kinda like it... And always add a comment to end as well (Toggle Plain Text) namespace blah { ... }; //namespace blah namespace blah { ... }; //namespace blah I might have an old backup on my flash disk, i'll have a look, if i find it i'll compile it and post the errror!

Sep 6th, 2007, 3:00 AM	#4
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	Found it. Hey, here's the exact error: (Toggle Plain Text) /tmp/cc1uTVHE.o(.bss+0x3d0): multiple definition of `Mathematics::TVector<double>::kZero' /tmp/ccDuSaWS.o(.bss+0x3d0): first defined here /tmp/cc1uTVHE.o(.bss+0x3e8): multiple definition of `Mathematics::TVector<double>::kZAxis' /tmp/ccDuSaWS.o(.bss+0x3e8): first defined here /tmp/cc1uTVHE.o(.bss+0x400): multiple definition of `Mathematics::TVector<double>::kYAxis' /tmp/ccDuSaWS.o(.bss+0x400): first defined here /tmp/cc1uTVHE.o(.bss+0x418): multiple definition of `Mathematics::TVector<double>::kXAxis' /tmp/ccDuSaWS.o(.bss+0x418): first defined here /tmp/cc1uTVHE.o(.bss+0x430): multiple definition of `Mathematics::TVector<float>::kZero' /tmp/ccDuSaWS.o(.bss+0x430): first defined here /tmp/cc1uTVHE.o(.bss+0x43c): multiple definition of `Mathematics::TVector<float>::kZAxis' /tmp/ccDuSaWS.o(.bss+0x43c): first defined here /tmp/cc1uTVHE.o(.bss+0x448): multiple definition of `Mathematics::TVector<float>::kYAxis' /tmp/ccDuSaWS.o(.bss+0x448): first defined here /tmp/cc1uTVHE.o(.bss+0x454): multiple definition of `Mathematics::TVector<float>::kXAxis' /tmp/cc1uTVHE.o(.bss+0x3d0): multiple definition of `Mathematics::TVector<double>::kZero' /tmp/ccDuSaWS.o(.bss+0x3d0): first defined here /tmp/cc1uTVHE.o(.bss+0x3e8): multiple definition of `Mathematics::TVector<double>::kZAxis' /tmp/ccDuSaWS.o(.bss+0x3e8): first defined here /tmp/cc1uTVHE.o(.bss+0x400): multiple definition of `Mathematics::TVector<double>::kYAxis' /tmp/ccDuSaWS.o(.bss+0x400): first defined here /tmp/cc1uTVHE.o(.bss+0x418): multiple definition of `Mathematics::TVector<double>::kXAxis' /tmp/ccDuSaWS.o(.bss+0x418): first defined here /tmp/cc1uTVHE.o(.bss+0x430): multiple definition of `Mathematics::TVector<float>::kZero' /tmp/ccDuSaWS.o(.bss+0x430): first defined here /tmp/cc1uTVHE.o(.bss+0x43c): multiple definition of `Mathematics::TVector<float>::kZAxis' /tmp/ccDuSaWS.o(.bss+0x43c): first defined here /tmp/cc1uTVHE.o(.bss+0x448): multiple definition of `Mathematics::TVector<float>::kYAxis' /tmp/ccDuSaWS.o(.bss+0x448): first defined here /tmp/cc1uTVHE.o(.bss+0x454): multiple definition of `Mathematics::TVector<float>::kXAxis' From this source: (Toggle Plain Text) #pragma once //local dependencies #include "Config.hpp" #include "Types.hpp" namespace App { namespace Mathematics { //forward declaritions template<typename T> class TMath; template<typename T> class TPoint; template<typename T> class ITEM TVector { public: //... //static members ITEM static const TVector<T> kXAxis; ITEM static const TVector<T> kYAxis; ITEM static const TVector<T> kZAxis; ITEM static const TVector<T> kZero; private: //data T vector[3]; protected: // }; //class TVector //static member declaritions //single precision template<> const TVector<Float> TVector<Float>::kXAxis(1.0f,0.0f,0.0f); template<> const TVector<Float> TVector<Float>::kYAxis(0.0f,1.0f,0.0f); template<> const TVector<Float> TVector<Float>::kZAxis(0.0f,0.0f,1.0f); template<> const TVector<Float> TVector<Float>::kZero(0.0f,0.0f,0.0f); //double precision template<> const TVector<Double> TVector<Double>::kXAxis(1.0,0.0,0.0); template<> const TVector<Double> TVector<Double>::kYAxis(0.0,1.0,0.0); template<> const TVector<Double> TVector<Double>::kZAxis(0.0,0.0,1.0); template<> const TVector<Double> TVector<Double>::kZero(0.0,0.0,0.0); ///members go here }; //namespace Mathematics }; //namespace App #pragma once //local dependencies #include "Config.hpp" #include "Types.hpp" namespace App { namespace Mathematics { //forward declaritions template<typename T> class TMath; template<typename T> class TPoint; template<typename T> class ITEM TVector { public: //... //static members ITEM static const TVector<T> kXAxis; ITEM static const TVector<T> kYAxis; ITEM static const TVector<T> kZAxis; ITEM static const TVector<T> kZero; private: //data T vector[3]; protected: // }; //class TVector //static member declaritions //single precision template<> const TVector<Float> TVector<Float>::kXAxis(1.0f,0.0f,0.0f); template<> const TVector<Float> TVector<Float>::kYAxis(0.0f,1.0f,0.0f); template<> const TVector<Float> TVector<Float>::kZAxis(0.0f,0.0f,1.0f); template<> const TVector<Float> TVector<Float>::kZero(0.0f,0.0f,0.0f); //double precision template<> const TVector<Double> TVector<Double>::kXAxis(1.0,0.0,0.0); template<> const TVector<Double> TVector<Double>::kYAxis(0.0,1.0,0.0); template<> const TVector<Double> TVector<Double>::kZAxis(0.0,0.0,1.0); template<> const TVector<Double> TVector<Double>::kZero(0.0,0.0,0.0); ///members go here }; //namespace Mathematics }; //namespace App Is it because i'm declaring static members in the header file? Hope you can help! Thanks!

Sep 6th, 2007, 7:40 AM	#6
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	Hey Grumpy! Thanks for the reply! Ok, i'll do that! (Toggle Plain Text) //static member declaritions //static member declaritions Is this not the right terminology? Thanks!

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Sep 5th, 2007, 2:33 PM	#2
Cache Hobbyist Join Date: Sep 2005 Posts: 261 Rep Power: 4	Works in VC8 (MSVC 2005) with no errors. Perhaps the 'once' pragma is meaningless in your environment? BTW, C++ doesn't require a semicolon to terminate a namespace.

Sep 6th, 2007, 7:11 AM	#5
grumpy Programming Guru Join Date: Jun 2005 Location: Adelaide, South Australia Posts: 1,223 Rep Power: 5	Yes, it is because you're defining the statics in the header file (or, more accuratly, because you're defining them in the header and then including that header in multiple source files [aka non-header files]). Move the definitions (which are after the comment that says "//static member declaritions" (sic)) so they only appear in a single source file.

Sep 7th, 2007, 2:09 AM	#7
rwm Professional Programmer Join Date: Jan 2007 Location: Cape Town Posts: 291 Rep Power: 2	Well that fixed the problem! Thanks man!

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