[boost] [python] type attributes in forward declarations

Class declarations like this... class BOOST_PYTHON_DECL wrapper_base; are causing compiler warnings on gcc 4.0.2 with a warning like: type attributes are honored only at type definition However, I see this is also used to handle the insane import/export windows DLL stuff. Since I do not do much compilation on the windows platforms anymore, is the BOOST_PYTHON_DECL really necessary in the forward declaration, or is it just a convention? Thanks!