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Jamie Webb wrote:
I agree that __gc metamethods for tables would be very useful, but there are complications: the reason AIUI that tables do not have them is because a destructor might create new references to an object. Unless Lua code can somehow be prevented from setting __gc (it's not sufficient to require that it be a C function), probably the only good solution is to move to a two-stage destruction, where the object has to be shown unreachable again after the destructor has been called. This is how Java does it.
__gc metamethods for tables are fairly easily fakeable -- I do it by using a mapping table to associate weak-refs of the table to a heavy userdata with the appropriate gc method attached to it. I'm fuzzy on whether this indirectly allows resurrection of the original table; to date I don't think I've had to worry about that. IIRC I've asked on this list in the past whether it was safe for a destructor to create new references, and was told that was fine. __gc on a table is useful for the same reasons that one might unify (heavy) userdata and tables, I think. I use it so that I can have the flexibility of a table attached to a C-side light userdata and still have my C-side objects gc'd. --Adam -- Adam D. Moss . ,,^^ adam@gimp.org http://www.foxbox.org/ co:3