Re: [RFC v2 1/2] compiler: use compiler to detect integer overflows

[Linus Torvalds]

On Wed, Nov 26, 2014 at 3:58 PM, Sasha Levin <sasha.levin@xxxxxxxxxx> wrote:
> We've used to detect integer overflows by causing an overflow and testing the
> result. For example, to test for addition overflow we would:

So I don't like this, for a very simple reason: it doesn't work for
older gcc versions.

Your "check_add_overflow()" doesn't actually do it. It just
perpetuates any bugs you find. For unsigned additions, it's pointless,
and for signed additions it remains as buggy as it was before.

Also, your commit message is still *very*wrong*. You can't claim that
integer addition overflow is undefined. It's undefined onyl for
_signed_ integer types, and that's a big big difference.

So no. This still doesn't work.

                     Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/