Re: string.gsub accepting a callable userdata

[David Favro <lua@...>]

On 12/13/2012 01:02 PM, Jerome Vuarand wrote:

> To avoid the creation of a closure on each call, you can cache one:
>
> local gsub,type = string.gsub,type
> local ref = setmetatable({}, {__weak='v'})
> local function unref(...) return ref[1](...) end
>
> function string.gsub(s,pat,repl)
>     if type(repl) == 'userdata' then
>        ref[1] = repl
>        repl = unref
>     end
>     return gsub(s,pat,repl)
> end

Wouldn't this be non-reentrant should the called userdata itself call gsub() 
[or cause it to be called via loaded script]?  ref[1] would now be the inner 
gsub()'s repl, and when the outer gsub() finds another match it will call 
unref() again which will dereference to the wrong repl.