utility class for the cheapest form of (light) userdata

template <typename T>
struct user;

template <typename T>
struct light;

sol::user<T> and sol::light<T> are two utility classes that do not participate in the full sol::usertype<T> system. The goal of these classes is to provide the most minimal memory footprint and overhead for putting a single item and getting a single item out of Lua. sol::user<T>, when pushed into Lua, will create a thin, unnamed metatable for that instance specifically which will be for calling its destructor. sol::light<T> specifically pushes a reference / pointer into Lua as a sol::type::lightuserdata.

If you feel that you do not need to have something participate in the full usertype<T> system, use the utility functions sol::make_user( ... ) and sol::make_light( ... ) to create these types and store them into Lua. You can get them off the Lua stack / out of the Lua system by using the same retrieval techniques on get and operator[] on tables and with stack operations.

Both have implicit conversion operators to T* and T&, so you can set them immediately to their respective pointer and reference types if you need them.