linux-kernel - Re: [GIT PULL] core/locking changes for v3.1

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Message-ID: <CA+55aFyDufcXR62j=crthVkNybk5is+c-zzr+LRmj_QSUskfmg@mail.gmail.com>
Date:	Mon, 25 Jul 2011 12:48:48 -0700
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaud Lacombe <lacombar@...il.com>,
	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [GIT PULL] core/locking changes for v3.1

On Mon, Jul 25, 2011 at 12:04 PM, Ingo Molnar <mingo@...e.hu> wrote:
> ..
> net/netfilter/nf_conntrack_core.c: In function ‘nf_conntrack_init’:
> net/netfilter/nf_conntrack_core.c:1579:3: warning: the comparison
> will always evaluate as ‘true’ for the address of
> ‘nf_conntrack_attach’ will never be NULL [-Waddress]

These all seem to be essentially compiler bugs.

We have macros that do generic things (in this case
"rcu_assign_pointer()" and tests their values. The fact that the tests
sometimes end up being statically true (or false) is not something the
compiler should complain about - it should use it to optimize the
code.

Sad.

We can make a compiler bug-report, or disable -Waddress. Or maybe we
can write the tests in a way that doesn't trigger the compiler bug.

This same issue is why I hated -Wsign-compare. Some of the things gcc
complained about were just technically moronic. So compiler warnings
are not always a good thing.

                  Linus
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