staticMetaObject

[dresha48]

Small addition:
if you already have big project where you get such errors (I think it only could happens if you are changing yours projects from qt3 to qt4) - just use for parent classes different macro (not like for the children) , where you got errors - thats all . For exapmle I added for all parents which gives me LNK2001 error :
add to parent classes from same dll ( in dll project property add to C/C++ ->Prprocessor->Preprocessor Definitions : DVL_DVL2_DLL_API; ):

#include "dllDefines.h"

class DVL_DVL2_API someParentClassName{...};

dllDefines.h :

#ifdef DVL_DVL2_DLL_API
#define DVL_DVL2_API __declspec(dllexport)
#else
#define DVL_DVL2_API __declspec(dllimport)
#endif