#ifdef LOG_EXPORTS
#define LOG_API __declspec(dllexport)
#else 
#define LOG_API __declspec(dllimport)
#endif

class LOG_API Log :
    public ofstream
{
public:
     Log(const char* szFn=DEFAULT_LOG_FILE,openmode om=DEFAULT_OPEN_MODE);
     int openLog(const char* szFn=DEFAULT_LOG_FILE,openmode om=DEFAULT_OPEN_MODE);
//    ifstream& operator <<(const char* szMsg); 
//    ifstream& operator <<(unsigned n); 
public:
    void closeLog(); 
    ~Log(void);
};

error C2470: 'Log' : looks like a function definition, but there is no parameter list; skipping apparent body

А>#ifdef LOG_EXPORTS
А>#define LOG_API __declspec(dllexport)
А>#else 
А>#define LOG_API __declspec(dllimport)
А>#endif
А>

А>class LOG_API Log :
А>    public ofstream
А>{
А>public:
А>     Log(const char* szFn=DEFAULT_LOG_FILE,openmode om=DEFAULT_OPEN_MODE);
А>     int openLog(const char* szFn=DEFAULT_LOG_FILE,openmode om=DEFAULT_OPEN_MODE);
А>//    ifstream& operator <<(const char* szMsg); 
А>//    ifstream& operator <<(unsigned n); 
А>public:
А>    void closeLog(); 
А>    ~Log(void);
А>};
А>

А>error C2470: 'Log' : looks like a function definition, but there is no parameter list; skipping apparent body
А>

в dll

class cLog
{
................
}
потом в .cpp

cLog  theLog; //он может быть как статический, так и можно его постоянно создовать через new при вызове GetLog
extern "C" __declspec(dllexport) cLog * PASCAL  GetLog()
{
    
    return &theLog;
}

GetProcAddress( m_hModule, "_GetLog@0" ) )

class A
{
__declspec(export) A();
__declspec(export) ~A();
};