Recently I want to use dlm to wrap all the c++ functions to read .dwg format file ! First, I made a simple start to begin with one object of polyline. then I construct the polyline struct as this: struct AcDbPolyline{ IDL_LONG numverts; IDL_LONG color[3]; double* vertices; IDL_STRING layer; }; because vertices' number is uncertain,so I made it a pointer ! the other fields can be easily done. I do not find any example in "calling c from IDL" in chapter 7 that can teach me to deal with the problem ! I am eager to known how can you all smart guys can do this when creating IDLFFDXF object and its entity,such as IDL_DXF_POLYLINE ! VERTICES Pointer (to an array of 3-D points) CONNECTIVITY Pointer (to an array of integers) VERTEX_COLORS Pointer (to an array of integers) how should I deal with the pointer in dll ! hoping for your early reply!