[Jyaif]

Jesus christ, 40% waste in arrays that can be solved by using `__attribute__((packed))`.

Irresponsible of them of not advertising this as an option in luaconf.h

[sfpotter]

Here's the rest of that paragraph for you:

"However, this attribute is a gcc extension not present in ISO C. Moreover, even in gcc it is not guaranteed to work [3]. As portability is a hallmark of Lua, this almost magical solution is a no-go."

[ethan_smith]

`__attribute__((packed))` wouldn't help here since the issue is about Lua's array/hash hybrid table design and memory allocation strategy, not C struct padding.

[lifthrasiir]

But it did help in the other way, in my reading of the paper [1]. So the OP is asking why this is not even an option on supported environments, and I too think that this is indeed a good question to ask.

[1] "Hugo Gualandi reported that just adding the gcc attribute __attribute__((packed)) to the definition of the structure TValue reduces its size from 16 to 9 bytes, without any sensible difference in performance."

[hugomg]

We figured that it wasn't worth dealing with the hassle of unaligned addresses because the more portable alternatives worked just as well.