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how to define a static member in a template class

i have trouble to define a static member in a template, and i search from google, but didn't find any similar case, my case is a little complex, i paste the code below.

code in xxx.h

Code:

template <class T> class FreeListManager

{

 public:

  FreeListManager(int s=0);

  ~FreeListManager();

  T* acquire();

  void release(T*);



 protected:

  static list<T*> freeList;

  static list<T*> usedList;

  // We have size parameters separated from list, since

  // size() function of list container is inefficient.



};

code in xxx.cpp

Code:

template<class T> list<T*>

  FreeListMaager<T>::freeList;

template<class T> list<T*>

  FreeListManager<T>::usedList;



//there is no T defined

for the xxx.cpp file, actually, it is confused me a lot, and it seem to be not what i want, what is the type of the entry in freeList like? i got coredump when use the freeList.pushback. and i ever tried to define the two list static member like

Code:

template<class CLASSA> list<CLASSA*>

  FreeListManager<CLASSA>::freeList;

template<class CLASSA> list<CLASSA*>

  FreeListManager<CLASSA>::usedList;



template<class CLASSB> list<CLASSB*>

  FreeListManager<CLASSB>::freeList;

template<class CLASSB> list<CLASSB*>

  FreeListManager<CLASSB>::usedList;

i got redefinition for freeList and usedList error.
i was told FreeListManager<CLASSA> and FreeListManager<CLASSB> are totally two different class, why does the redefinition error come out?

i also try

Code:

list<CLASSA*> FreeListManager<CLASSA>::freeList;

list<CLASSA*> FreeListManager<CLASSA>::usedList;



list<CLASSB*> FreeListManager<CLASSB>::freeList;

list<CLASSB*> FreeListManager<CLASSB>::usedList;

i got too few template-parameter-lists error, the code can be compiled on gcc earlier version,

can someone help me, really appreciate your help.

denny

Are you sure that you want to use static? This means that there is only one instance of the data member; controlled by the class. Should you wish to create two instances of FreeListManager with the same template parameter then you will lose the second list.

But to address your question first note that for templates the definition and the declaration need to be in the same header file.

I would suggest that you make your lists pointers, thus you will have:

Code:

static list<T*> *freeList;

Initialise it will then be:

Code:

template<class T> list<T*> *FreeListManager<T>::freeList = 0;

sure, that's what i want, the code was download from opendiameter project, it can be compiled by very old version gcc complier.

but i found it cannot compliled by gcc-4.1.2.

yes, i include the xxx.h file in the xxx.cpp file.

As i know, FreeListManager is a only template, and FreeListManager<CLASSA> is actual class, and FreeListManager<CLASSB> is another one, i want to define two static list member for both class,FreeListManager<CLASSA>::freeList, FreeListManager<CLASSB>::freeList, so the two static member should be not one instance, but two. Just like what i tested

Code:

template <class T> class FreeListManager

{

 public:

  static int counter;

};



template <class T> int FreeListManager<T>::counter=0;

//the following definition will report redefinition error, either

//template <CLASSA> int FreeListManager<CLASSA>::counter=0;

//template <CLASSB> int FreeListManager<CLASSB>::counter=0;

//i thought the complier only can initial the two static member once, and you can set other value later.



FreeListManager<CLASSA>::counter=2

FreeListManager<CLASSB>::counter=3



main()

{

  printf("FreeListManager<CLASSA>::counter=%d\n",FreeListManager<CLASSA>::counter);

  printf("FreeListManager<CLASSB>::counter=%d\n",FreeListManager<CLASSB>::counter);

}

##########################
the result is
FreeListManager<CLASSA>::counter=2
FreeListManager<CLASSB>::counter=3

so it seem there are two static variable FreeListManager<CLASSA> and FreeListManager<CLASSB>

i also tried

template<> list<CLASSA>
FreeListManager<CLASSA>::freeList;
template<> list<CLASSA>
FreeListManager<ACLASSA>::usedList;
template<> list<CLASSB>
FreeListManager<CLASSB>::freeList;
template<> list<CLASSB>
FreeListManager<CLASSB>::usedList;

i aslo got undefined reference error

for the gcc compiler "the definition and the declaration need to be in the same header file." That's NOT include the header file in a source but actually placed in the header file.