RE: Can I use __gc metamethod directly from Lua?

["Ram Firestone" <bichir@...>]

I'm still not sure of your application; however tables will "self clean" on their own. The __GC method just doesn't get called on
them because it's not necessary. 

Perhaps you are storing userdata items in your table? If this is the case the __GC method will be called for each userdata item in
your table separately (assuming it has one) before the table is destructed. So you can do your memory clean up there. 

I'll just assume you are doing something that is beyond my experience because other than some garbage collection tracking
application I don't see a reason for __GC method on a table. I'm not even sure what code you would put there.

> -----Original Message-----
> From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-bounces@bazar2.conectiva.com.br] On Behalf Of
> joseph stewart
> Sent: Saturday, November 25, 2006 3:35 PM
> To: Lua list
> Subject: Re: Can I use __gc metamethod directly from Lua?
> 
> > I'm just curious. Why do you need a __GC method for a table anyway?
> > I tend to always use this for C++ classes where I need to call
> > the destructor.
> >
> 
> As I mentioned, I'm trying to move some of the gruntwork from the 'C'
> side to the Lua side. Without going into too many details, I have low-
> level "allocation" functions callable by Lua that have items that
> need corresponding "de-allocate" functions to avoid memory leaks. My
> Lua-side code handled creating tables that I'd hoped could "self-
> clean" during the collection cycle.
> 
> I'm familiar with doing this on the 'C' side, I was just trying to
> minimize the 'C' code.
> 
> -joe
> 
> >> -----Original Message-----
> >> From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-
> >> bounces@bazar2.conectiva.com.br] On Behalf Of
> >> joseph stewart
> >> Sent: Saturday, November 25, 2006 3:15 PM
> >> To: Lua list
> >> Subject: Re: Can I use __gc metamethod directly from Lua?
> >>
> >>
> >> On Nov 25, 2006, at 6:09 PM, Ram Firestone wrote:
> >>
> >>> __gc only works for userdata values.
> >>>
> >>
> >> Ah, I was working off the info at:
> >>
> >> http://lua-users.org/wiki/MetatableEvents
> >>
> >> That stinks. There's a lot of busy-work in C that I'd rather do in
> >> Lua. Too bad.
> >>
> >> Thanks for the correction.
> >>
> >> -joe
> >>
> >>>> -----Original Message-----
> >>>> From: lua-bounces@bazar2.conectiva.com.br [mailto:lua-
> >>>> bounces@bazar2.conectiva.com.br] On Behalf Of
> >>>> joseph stewart
> >>>> Sent: Saturday, November 25, 2006 3:05 PM
> >>>> To: Lua list
> >>>> Subject: Can I use __gc metamethod directly from Lua?
> >>>>
> >>>> Hello all,
> >>>>
> >>>> I'm developing a library binding and to minimize the amount of 'C'
> >>>> code I need to write, I want to have Lua handle the __gc
> >>>> metamethod.
> >>>> At first glance, this doesn't appear to do what I want. Here's the
> >>>> essence of what I'm doing:
> >>>>
> >>>> mt = {}
> >>>> mt.__gc = function() print("gc me") end
> >>>> t = {1,2,3}
> >>>> setmetatable(t, mt)
> >>>> t = nil
> >>>> collectgarbage("collect")
> >>>>
> >>>> I would expect to see "gc me" printed after the collectgarbage
> >>>> function call, but I don't.
> >>>>
> >>>> Am I completely on the wrong track? I've used __gc from 'C' code
> >>>> and
> >>>> more or less get what I expect. Is __gc usable from Lua code?
> >>>>
> >>>> Thanks in advance for any help! When the library is done, I'll
> >>>> share
> >>>> it with y'all.
> >>>>
> >>>> -joe
> >>>
> >