Exporting static data in a DLL
- by Gayan
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
