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From: Andrew Morton <akpm@linux-foundation.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Christophe de Dinechin <dinechin@redhat.com>,
	trivial@kernel.org, Ben Segall <bsegall@google.com>,
	"Michael S. Tsirkin" <mst@redhat.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Ingo Molnar <mingo@redhat.com>, Mel Gorman <mgorman@suse.de>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Vincent Guittot <vincent.guittot@linaro.org>,
	Paolo Bonzini <pbonzini@redhat.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Jason Wang <jasowang@redhat.com>,
	virtualization@lists.linux-foundation.org,
	linux-kernel@vger.kernel.org,
	Zhen Lei <thunder.leizhen@huawei.com>,
	Juri Lelli <juri.lelli@redhat.com>
Subject: Re: [PATCH 1/3] sched/headers: Fix compilation error with GCC 12
Date: Thu, 14 Apr 2022 13:30:50 -0700	[thread overview]
Message-ID: <20220414133050.b820fa45d42de4cfc24db82b@linux-foundation.org> (raw)
In-Reply-To: <Ylg73c83AJGwz9UN@hirez.programming.kicks-ass.net>

On Thu, 14 Apr 2022 17:21:01 +0200 Peter Zijlstra <peterz@infradead.org> wrote:

> > +/* The + 1 below places the pointers within the range of their array */
> >  #define for_class_range(class, _from, _to) \
> > -	for (class = (_from); class != (_to); class--)
> > +	for (class = (_from); class + 1 != (_to) + 1; class--)
> 
> Urgh, so now we get less readable code, just because GCC is being
> stupid?
> 
> What's wrong with negative array indexes? memory is memory, stuff works.

What's more, C is C.  Glorified assembly language in which people do odd
stuff.

But this is presumably a released gcc version and we need to do
something.  And presumably, we need to do a backportable something, so
people can compile older kernels with gcc-12.

Is it possible to suppress just this warning with a gcc option?  And if
so, are we confident that this warning will never be useful in other
places in the kernel?

If no||no then we'll need to add workarounds such as these?

  reply	other threads:[~2022-04-14 20:30 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-04-14 15:08 [PATCH 0/3] trivial: Fix several compilation errors/warnings with GCC12 Christophe de Dinechin
2022-04-14 15:08 ` [PATCH 1/3] sched/headers: Fix compilation error with GCC 12 Christophe de Dinechin
2022-04-14 15:21   ` Peter Zijlstra
2022-04-14 20:30     ` Andrew Morton [this message]
2022-04-17 15:52       ` Peter Zijlstra
2022-04-20 18:45         ` Kees Cook
2022-04-21  7:32           ` Peter Zijlstra
2022-04-25 14:23       ` Christophe de Dinechin
2022-04-17 13:27     ` David Laight
2022-04-25 14:07     ` Christophe de Dinechin
2022-05-19 11:16       ` Peter Zijlstra
2022-04-14 15:08 ` [PATCH 2/3] nodemask.h: Fix compilation error with GCC12 Christophe de Dinechin
2022-04-14 15:23   ` Peter Zijlstra
2022-04-14 15:08 ` [PATCH 3/3] virtio-pci: Use cpumask_available to fix compilation error Christophe de Dinechin
2022-04-15  8:48   ` Michael S. Tsirkin
2022-04-28  9:48     ` Christophe Marie Francois Dupont de Dinechin
2022-04-28 11:06       ` Michael S. Tsirkin
2022-05-15 21:24 ` [PATCH 0/3] trivial: Fix several compilation errors/warnings with GCC12 Davidlohr Bueso

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