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Date:      Sun, 6 Nov 2011 17:36:06 -0700
From:      Warner Losh <imp@bsdimp.com>
To:        Rui Paulo <rpaulo@FreeBSD.org>
Cc:        Alexander Best <arundel@FreeBSD.org>, freebsd-toolchain@FreeBSD.org, Dimitry Andric <dim@FreeBSD.org>
Subject:   Re: [poc] buildkernel + clang + -Werror
Message-ID:  <242747B7-3EAE-4988-A975-DC58B0997A6F@bsdimp.com>
In-Reply-To: <C7A0F95A-0F55-47BF-AD60-66DDAEEC3EC7@FreeBSD.org>
References:  <20111105102102.GA54596@freebsd.org> <20111106172835.GO2258@hoeg.nl> <20111106203316.GA73216@freebsd.org> <4EB6F38E.2080006@FreeBSD.org> <20111106205805.GA78142@freebsd.org> <C7A0F95A-0F55-47BF-AD60-66DDAEEC3EC7@FreeBSD.org>

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On Nov 6, 2011, at 2:13 PM, Rui Paulo wrote:
> The only argument against this tautological check that I agree with is =
when the code is explicitly trying to be safe. If the developer checks =
for "i < 0" when indexing an array he/she is trying to guard against =
possible pitfalls in the future when someone suddenly decides to change =
the variable type to become signed. One possible security vulnerability =
was avoided because that developer checked for negative values.
> I'm against turning this off by default, but it should not cause an =
error.

Except when you pass args back and forth between signed and unsigned and =
back again.  If you check < 0 in the middle, that's one more security =
bug you thought you had fixed, but really you've done nothing with.

Warner




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