very dangours waring

There are so many warning C4251!
plz fix!
7>e:-prj\igame\trunk\engine\cocos2dx\label_nodes\cclabelbmfont.h(182): warning C4251: ‘cocos2d::CCLabelBMFont::m_sFntFile’ : class ‘std::basic_string<*Elem,*Traits,*Ax>’ needs to have dll-interface to be used by clients of class ’cocos2d::CCLabelBMFont’
7> with
7> [
7>*Elem=char,
7> *Traits=std::char_traits,
7>*Ax=std::allocator
7> ]
7>e:-prj\igame\trunk\engine\cocos2dx\label_nodes\cclabelbmfont.h(185): warning C4251: ’cocos2d::CCLabelBMFont::m_sInitialString’ : class ’std::basic_string<*Elem,*Traits,*Ax>‘needs to have dll-interface to be used by clients of class ’cocos2d::CCLabelBMFont’
7> with
7> [
7>*Elem=char,
7> *Traits=std::char_traits,
7>*Ax=std::allocator
7> ]