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Date:      Fri, 20 Jul 2012 19:33:52 +0300
From:      Konstantin Belousov <kostikbel@gmail.com>
To:        Dimitry Andric <dim@freebsd.org>
Cc:        freebsd-current@freebsd.org, Kim Culhan <w8hdkim@gmail.com>
Subject:   Re: -current build failure
Message-ID:  <20120720163352.GS2676@deviant.kiev.zoral.com.ua>
In-Reply-To: <50097BF0.9010103@FreeBSD.org>
References:  <CAKZxVQV5xhFDN_WbTk-EMoQ18N8u1f4YhqKSJQFUzbX4NZxhUA@mail.gmail.com> <50097BF0.9010103@FreeBSD.org>

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On Fri, Jul 20, 2012 at 05:40:32PM +0200, Dimitry Andric wrote:
> On 2012-07-20 16:49, Kim Culhan wrote:
> >  Seeing this for r:238655
> ...
> > In file included from /usr/src/sys/modules/dtrace/dtrace/../../../sys/p=
cpu.h:44:
> > ./machine/pcpu.h:226:13: error: indirection of non-volatile null
> > pointer will be deleted, not trap
> >       [-Werror,-Wnull-dereference]
> >             : "m" (*(char *)OFFSETOF_CURTHREAD));
> >                    ^~~~~~~~~~~~~~~~~~~~~~~~~~~
> > ./machine/pcpu.h:226:13: note: consider using __builtin_trap() or
> > qualifying pointer with 'volatile'
>=20
> That's indeed a valid warning from clang, since OFFSETOF_CURTHREAD is
> usually zero.  It's probably due to recent work on dtrace.  I'm not in
> the neighborhood of a FreeBSD box right now to verify, but can you
> please try to change the cast to "(volatile char *)"?  That should fix
> the warning.

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.

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