Function dwg_dynapi_subclass_value 

pub unsafe extern "C" fn dwg_dynapi_subclass_value(
    ptr: *const c_void,
    subclass: *const c_char,
    fieldname: *const c_char,
    out: *mut c_void,
    fp: *mut Dwg_DYNAPI_field,
) -> bool

Returns the common OBJECT.subclass.fieldname value in out. ptr points to the subclass field. The optional Dwg_DYNAPI_field *fp is filled with the field types from dynapi.c