Import/Export singleton class between multiple files

I am trying to create a thread safe singleton class(MySingleton). A.h contains declaration and A.cpp has definitions. I need to use this singleton object in B.cpp and C.cpp which are both getting compiled into different DLLs. In B.cpp I want to set the variable ptrval and in C.cpp I am retrieving variable ptrval.

In A.h

class MySingleton {
public:

    static MySingleton* getInstance();
    void setval(int* uid);
    int* getval();


private:
    MySingleton() = default;
    ~MySingleton() = default;
    MySingleton(const MySingleton&) = delete;
    MySingleton& operator=(const MySingleton&) = delete;
    int* ptrval = nullptr;
    static MySingleton* instance;
};

#ifdef MySingleton_DLLEXPORT
extern __declspec(dllexport) int* ptrval = nullptr;
extern __declspec(dllexport) MySingleton* getInstance();
extern __declspec(dllexport) void setval(int* uid);
extern __declspec(dllexport)  int* getval();
extern __declspec(dllexport)  MySingleton* instance = 0;
#else
extern __declspec(dllimport) int* ptrval;
extern __declspec(dllimport) MySingleton* getInstance();
extern __declspec(dllimport) void setval(int* uid);
extern __declspec(dllimport)  int* getval();
extern __declspec(dllimport)  MySingleton* instance;
#endif

In A.cpp

#pragma push_macro("MySingleton_DLLEXPORT")
#define MySingleton_DLLEXPORT
#include <A.h>
#pragma pop_macro("MySingleton_DLLEXPORT")

MySingleton* MySingleton::instance;

MySingleton*  MySingleton::getInstance()
{
    if (instance == 0)
        instance = new MySingleton();
    return instance;
}

void MySingleton::setval(int* uid) {
    this->ptrval = uid;
}

int* MySingleton::getval() {
    return this->ptrval;
}

In B.cpp

#pragma push_macro("MySingleton_DLLEXPORT")
#include <A.h>
#pragma pop_macro("MySingleton_DLLEXPORT")

int* uid = (getting uid from a function)
(MySingleton::getInstance())->setval(uid);

In C.cpp

#pragma push_macro("MySingleton_DLLEXPORT")
#include <A.h>
#pragma pop_macro("MySingleton_DLLEXPORT")

ptrval = (MySingleton::getInstance())->getval();

I am getting the following linking error: B.obj : error LNK2019: unresolved external symbol "public: static class MySingleton* __cdecl MySingleton::getInstance(void)"

Any help would be appreciated!