Re: In praise of globals

[Philipp Janda <siffiejoe@...>]

Am 18.04.2013 02:43 schröbte Steve Litt:
> On Wed, 17 Apr 2013 22:42:38 +0200
> Dirk Laurie <dirk.laurie@gmail.com> wrote:
>
> > 2013/4/17 Steve Litt <slitt@troubleshooters.com>:
> >
> >
> > > Is there any way to protect every last bit of _ENV? If so, I could
> > > run the program and see every place where a global is being set.
> >
> > Sure, see Programming in Lua by Roberto Ierusalimschy,
> >
> >     13.4.4 – Tracking Table Accesses.
> >
> > http://www.lua.org/pil/13.4.4.html
>
> Thanks Dirk,
>
> That didn't work out quite as well as I'd hoped. It works just fine
> with a global table named t, but when I change it to _G, it doesn't
> work. Here's the program:
>
> #!/usr/bin/lua
>
> globalfname='Steve'
> globallname='Litt'
>
> -- keep a private access to original table
> local _forbidden = _G
>
> -- create proxy
> _G = {}

That won't work, since _G is just an additional reference to (the value 
returned by) getfenv() or _ENV (depending on the Lua version). Changing 
it will only affect code that explicitly uses _G. For the rest you will 
have to replace the current environment using setfenv or assignment to _ENV.

Philipp