luaL_checkudata: Bug? Feature?

[Roger Ivie <rivie@...>]

I've noticed that luaL_checkudata cannot be used with a negative stack 
index; that is, one relative to the top of the stack. The difficulty
is that it fetches the metatable from the registry before it fetches
the metatable from the userdata to be checked, so the stack depth
has changed by the time it does that.

--
roger ivie
rivie@ridgenet.net