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On Thu, Nov 10, 2011 at 5:58 PM, Petite Abeille
<> wrote:
> On Nov 10, 2011, at 6:20 PM, Peter Cawley wrote:
>> It is also impossible to write setfenv in 5.2 in such a way as to work
>> with bytecode chunks whose debug information has been stripped.
> Why? _ENV is always the first upvalue, no? No need to look it up by name, no? Its position will suffice, no?

No, no and no. :)

_ENV is only the first upvalue for a function that was compiled from a
top-level source code chunk. Functions *in general*, i.e. also
including functions defined inside a chunk or other function, may have
_ENV at a different position, or even not at all.

This has been discussed before: