RE: Strings and GC - was RE: Using full userdata as table index?

[RLake@...]

> So - as far as memory usage goes, is it correct to say that if a string
> is not reachable by any means, weak table or otherwise, it will be
> collected?

Yes, eventually, probably.

Sorry I cannot be more precise than that, but that
is the way it is.

Lua does not aggressively garbage collect strings.
It also does not
aggressively garbage collect table keys. So they might
hang about for
a while.

Lightuserdata are like numbers: they don't actually
take up any
space because they are entirely contained within the
"reference".
(The reference takes up space, but no additional space
is taken
up by the object.) This also applies to nil, true
and false.

If you had an id whose value could be converted easily
into
something that could be cast to (void*), you would
be better
off using a lightuserdata, provided that you could
guarantee
that no other "type" of lightuserdata might
have the same
value. For example, if your id is actually the address
of a
foreign object, and all your lightuserdata are addresses
of
some object or another, then you could use a lightuserdata
instead of converting the id to a string. That would
reduce
your memory utilisation and save on garbage collection
time.

Hope that helps.
R.