Re: Singleton MFC Extension DLL

Stephen Myers <""StephenMyers\"">
Thu, 07 Jan 2010 12:52:37 -0600
Ajay Kalra wrote:

On Jan 7, 1:05 pm, MFDonadeli <> wrote:

On 7 jan, 16:01, Ajay Kalra <> wrote:

On Jan 7, 12:54 pm, MFDonadeli <> wrote:

I declare a singleton on a MFC extension DLL, like this:
//header file: SingleTon.h
class AFX_EXT_CLASS CMySingleton
  static CMySingleton* Instance()
                singleton = new CMySingleton();
    return singleton;
  int a;
// Other non-static member functions
  CMySingleton() {}; // Private
  CMySingleton(const CMySingleton&); // Prevent copy-
  CMySingleton& operator=(const CMySingleton&); // Prevent
  virtual ~CMySingleton() {};
  static CMySingleton* singleton;
And in a cpp file I code the following line:
CMySingleton* CMySingleton::singleton = NULL;
Code 2:
CMySingleton *a;
a = CMySingleton::Instance();
The problem is when I code "code 2" in a Regular Dll, all works fine,
but when I code "code 2" in another MFC extension DLL gives an error:
unresolved external symbol "private: static class CMySingleton*
CMySingleton::singleton" (?singleton@CMySingleton@@0PAV1@A)
Any idea?

Are you sure you are including the correct .lib file in MFC extesion
DLL where you code2 sits?

Yes, via Project Dependencies on VS 2008...

As Joe already pointed out, it doesnt mean much in your case. All you
are ensuring is the build order as such. You need to somehow link to
the library you are trying to use.

How did this work for the Regular DLL for you? You would have the same
problem there as well.


I've got a large solution where project dependencies are added as linker

This may vary based on project types, where regular DLL's are added and
MFX Extensions are not. (I don't have any experience with MFC extensions.)

Check the Porject Properties/Linker/Command Line to see if your library
shows up.

If not add the .lib as a linker input.


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