Hi Alexandre, Taking Dima's solution in conjunction with the way Apple solved their similar problem by using opaque types in Cocoa and Carbon: struct CW_C_MsgUp_s; typedef struct CW_C_MsgUp_t* CW_C_MsgUp_t; struct CW_C_MsgDown_s; typedef struct CW_C_MsgDown_t* CW_C_MsgDown_t; This will insulate your implementation of those opaque types from the public header files (note that the structs are forward references, and not declared publically), and allow you some measure of type safety in C. Apple uses a factory function to create their opaque types, and for most opaque types the CFRelease function to destruct them (using a reference counting mechanism). That's the role that CW_C_MsgUp_new() and CW_C_MsgDown_new() provides. As far as them being pointers... I believe that you will want them to be pointers baked into the typedef. The one change to your code would be to change from this... CW_C_MsgUp_t *my_up_msg; CW_C_MsgDown_t *my_down_msg; ...to this... CW_C_MsgUp_t my_up_msg; CW_C_MsgDown_t my_down_msg; HTH, --Eljay
