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From: David Chisnall <theraven@FreeBSD.org>
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Date: Fri, 20 Jul 2012 22:07:05 +0100
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To: Konstantin Belousov <kostikbel@gmail.com>
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Cc: Kim Culhan <w8hdkim@gmail.com>, freebsd-current@FreeBSD.org,
	Dimitry Andric <dim@FreeBSD.org>
Subject: Re: -current build failure
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On 20 Jul 2012, at 17:33, Konstantin Belousov wrote:

> It is not related to dtrace at all, and indeed OFFSETOF_CURTHREAD is =
0.
> This is a bug in clang, we compile our kernel in freestanding =
environment.

The copies of the C spec that I have do not differentiate between =
freestanding and hosted environments for the validity of dereferencing a =
pointer value of 0.  Doing so is undefined in all cases and any =
standards-compliant compiler is quite at liberty to eat your dog in such =
situations - it is explicitly not guaranteed to read the memory at =
linear address 0 (this is undefined for at least two reasons that I can =
think of from the C spec, and probably more). =20

David=