file name char set string conversions

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@30586 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

include/wx/string.h

@@ -830,8 +830,11 @@ public:
 #if wxUSE_WCHAR_T
     const wxWCharBuffer wc_str(wxMBConv& conv) const;
 #endif // wxUSE_WCHAR_T
-
+#ifdef __WXOSX__
+    const wxCharBuffer fn_str() const { return wxConvFile.cWC2WX( wc_str( wxConvLocal ) ); }
+#else
     const wxChar* fn_str() const { return c_str(); }
+#endif
 #endif // Unicode/ANSI
 
   // overloaded assignment