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On 19/08/2016 01:48, ThePhD wrote:
Well, I looked into this deeper after everyone gave me the conventional wisdom to NOT depend on `lua_next`'s iteration order and pray for no breaking changes.
It turns out that the correct wisdom -- iterate using an index value 
-- seems to also be the most performant wisdom from the C++ or C side. 
[1] compares the performance of calling `lua_next()` in a while loop 
and assuming it iterates in the right order, pushing a table and 
calling `lua_geti` with the indices (and knowing the size and indices 
before hand), and the other measures the doing a lua_pushinteger + 
lua_gettable. Measured in a computer with an i7 Intel chip, lots of 
ram, Windows 10, Lua 5.3.3 compiled as a DLL.
Interestingly, the pushinteger + gettable method is about equal to the 
lua_next implementation. So, for Lua 5.2 and lower, since there's no 
lua_geti intrinsically built into the API, the correct way is equal in 
performance to the UB way.
There is however a lua_rawgeti method that you can use.

--Regards,
Liam