How reliable is lua_topointer() ?

[Lawrie Nichols <lawrien@...>]

I'm looking at using the pointer returned from lua_topointer() as an 
index into a weak-keyed table, but it's not obvious whether Lua might 
ever change these pointers during the execution of my scripts (ie 
whether a gc cycle might moving things around internally).

I'm guessing that for userdata, ghe pointer cannot be changed (since Lua 
has no way of knowing the relevance of the data pointed to in the 
userdata), but I'm not so sure whether this would hold true for 
functions/tables.

I've had a look at the PiL on lua_topointer(), and all that says is that 
the pointer cannot be used to to retrieve what was being pointed to.

To be honest, from trying it out, there doesn't seem to be any issues, 
but I'd like to be sure.

Thanks

Lawrie