Re: Dll containing class with static member, Linker error

From:
"Doug Harrison [MVP]" <dsh@mvps.org>
Newsgroups:
microsoft.public.vc.language
Date:
Tue, 25 Jul 2006 18:58:06 -0500
Message-ID:
<nqbdc29p4gf99hb1cdrgun0bkaismihrvt@4ax.com>
On Tue, 25 Jul 2006 16:43:02 -0700, deflagg
<deflagg@discussions.microsoft.com> wrote:

DllTest.h

#include <iostream>
using namespace std;
class __declspec(dllexport) CDllTest
{
public:
    CDllTest(){}
    ~CDllTest(){}

    void foo(){myint = new int();}

    static int* myint;
};

DllTest.cpp

int* CDllTest::myint = NULL;

This code is in a DLL called DllTest. When I try to link this dll to my
client app, I get a linker error. It is as follows:

Error 1 error LNK2001: unresolved external symbol "private: static int *
CDllTest::myint" (?myint@CDllTest@@0PAHA) DllTestApp.obj

I figured out if I put the intialization of myint into the header file along
with the class definition, it will link fine. It's only when I put the
intialization of myint in the cpp file. Yes I could just keep the
initialization in my cpp file, but that's not the point. The point is, why I
can't have it in my cpp file vs my header file. Thank's in advance for all
your help.


It absolutely should go into your .cpp file. Try dumpbin /exports on your
DLL and see if myint is exported, or use depends.exe. However, if that's
how you're really using dllexport, see this message for the proper way to
do it:

http://groups.google.com/group/microsoft.public.dotnet.languages.vc/msg/9c40e8ab9410eeb1

--
Doug Harrison
Visual C++ MVP

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