Re: Exporting static member functions

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.language

Date:

Mon, 03 Mar 2008 23:11:30 -0600

Message-ID:

<81mps3d9p3s7g4u5seutbri6vgm0vbblvn@4ax.com>

On Mon, 3 Mar 2008 17:11:33 -0800 (PST), carichardson3306@gmail.com wrote:

I've succcessfully created a DLL full of classes that I've exported to
use in another DLL. But I have a class that full of static member
functions and the function names arent resolving

When I try to create a new DLL, importing the class definitions, I get
unresolved external errors, but only for the static member functions.
Why is that?

Shouldnt the class be imported when its declared?

Below is the class definitions

devlibrary.h - Included in my stdafx.h for both DLLs
#define DEV_DLL_EXPORT __declspec ( dllexport )
#define DEV_DLL_IMPORT __declspec ( dllimport )

#ifdef _DEVLIBRARY_DLL
#define DEVLIBRARY_CLASS DEV_DLL_EXPORT
#else
#define DEVLIBRARY_CLASS DEV_DLL_IMPORT
#endif

cpstinterface.h
class DEVLIBRARY_CLASS CPSTDriverInterface
{
static short GetCnlVarsCount();
static CCnlVar *GetAllCnlVar(short var_rank);
static CCnlVar *GetAllCnlVar(char *szProtVarName);
}

main.cpp
#include "cpstdriverinterface.h"
{
...
dwNumOfVars = CPSTDriverInterface::GetCnlVarsCount();
...
}

Error

error LNK2001: unresolved external symbol "__declspec(dllimport)
public: static short __stdcall
CPSTDriverInterface::GetCnlVarsCount(void)" (__imp_?
GetCnlVarsCount@CPSTDriverInterface@@SGFXZ)

The error message thinks it's a public function, but your class declares it
private. Absent your real code, my best guess is that you forgot to define
the static functions in your DLL. In general, one of the first things to do
in situations like this is to see if the DLL actually exports the function,
so does dumpbin /exports shed any light? How about Dependency Walker?

--
Doug Harrison
Visual C++ MVP