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SubjectRe: [PATCH] BUILD_BUG_ON sucks


On Sat, 16 Aug 2008, Rusty Russell wrote:
>
> Interesting idea, but I've come to actually like the semantic explicitness of
> BUILD_BUG_ON. There's a difference between "we should never get here"
> and "this should never exist".

Agreed. I think Alexey's patch is broken.

The thing is, BUILD_BUG_ON() is a different thing. It says "this is a
build error", while BUG_ON() says "this is an error if we reach it".

Very different.

The fact that you broke BUG_ON(1) should have made you think. Sometimes
the "1" isn't necessarily a constant one. It might be

if (something_that_can_never_happen_in_some_configuration) {
...
BUG_ON(CONFIG_XYZZY);
...
}

where the BUG_ON(1) is absolutely *not* the same thing as BUILD_BUG_ON().

Linus


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