I have a DLL which contains a class with static members. I use __declspec(dllexport) in order to make use of this class's methods. But when I link it to another project and try to compile it, I get "unresolved external symbol" errors for the static data.

e.g. In DLL, Test.h

class __declspec(dllexport) Test{
protected:
    static int d;
public:
    static void m(){}
}

In DLL, Test.cpp

#include "Test.h"

int Test::d;

In the application which uses Test, I call m().

I also tried using __declspec(dllexport) for each method separately but I still get the same link errors for the static members.

If I check the DLL (the .lib) using dumpbin, I could see that the symbols have been exported.

For instance, the app gives the following error at link time:

1>Main.obj : error LNK2001: unresolved external symbol "protected: static int CalcEngine::i_MatrixRow" (?i_MatrixRow@CalcEngine@@1HA)

But the dumpbin of the .lib contains:

Version      : 0
  Machine      : 14C (x86)
  TimeDateStamp: 4BA3611A Fri Mar 19 17:03:46 2010
  SizeOfData   : 0000002C
  DLL name     : CalcEngine.dll
  Symbol name  : ?i_MatrixRow@CalcEngine@@1HA (protected: static int CalcEngine::i_MatrixRow)
  Type         : data
  Name type    : name
  Hint         : 31
  Name         : ?i_MatrixRow@CalcEngine@@1HA

I can't figure out how to solve this. What am I doing wrong? How can I get over these errors?

P.S. The code was originally developed for Linux and the .so/binary combination works without a problem