Re: Functions with individual metatables

[Richard Hundt <richardhundt@...>]

Henk Boom wrote:

> This doesn't work transparently, though, you have to be careful when
> using this implementation as it will introduce memory leaks in the
> presence of cycles.

Nice catch.

Since I've posted the code, I now feel obligated to maintain it :)

So I've given it a bit more thought, fixed some bugs in my previous post 
and simplified it. It'll still suffer the same leak with cycles, but 
these can now be factored out so:

setfmeta(f, {__index = function () return f end})

becomes:

setfmeta(f, {__index = function(t, k) return t.func end})

and the code:

local func_meta = { }
setmetatable(func_meta, { __mode = "k" })

debug.setmetatable(function() end, {
   __index = function(func, key)
      local meta = func_meta[func]
      if meta then
         return meta[key]
      end
   end;
   __newindex = function(func, key, val)
      local meta = func_meta[func]
      if meta then
         meta[key] = val
      end
   end;
})

function setfmeta(func, meta)
   func_meta[func] = setmetatable({ func = func }, meta)
   return func
end

function getfmeta(func)
   return getmetatable(func_meta[func])
end

Cheers,
Rich