Re: Question about debug.getupvalue

["Alex Davies" <alex.mania@...>]

> I have got a question about debug.getupvalue :
> why is it forbidden to get an upvalue value
> from a C function in Lua ?

It's merely a security thing. Lua should not be able to modify a C functions 
upvalues, which getupvalue would allow in the case of tables or userdata. Eg 
the common case of having a metatable as an upvalue. You're right though, 
for immutable types such as numbers and strings there'd be no danger. 
There's no harm in writing your own getupvalue using the C API though.

- Alex