Will upvalue 1 work if the loaded file doesn't reference any globals? On 20.05.2010 23:15, Roberto Ierusalimschy wrote:
With Lua 5.1, I have the following code : setfenv(level, M) With Lua 5.2.0 work2, I rewrite it as following (compatible with Lua 5.1) : debug.setfenv(debug.getinfo(level, 'f').func, M) Now, with Lua 5.2.0 work3, it becomes : if debug.setupvalue(debug.getinfo(level, 'f').func, 1, M) ~= '_ENV' then setfenv(level, M) -- Lua 5.1 end The value 1 seems magical, but I think _ENV is alway the first upvalue.Not necessarily. If the function is a main function (that is, the direct result of load) then _ENV is always the first (and only) upvalue and it is always present. Other functions have _ENV just like any other upvalue. For instance, consider the following code: local a function foo () return a + b end In function foo, the first upvalue is 'a' and the second is '_ENV'. -- Roberto
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