linux-kernel - Re: [PATCH] KVM: arm64: Drop 'const' from argument of vq

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Message-ID: <20190604095713.GV28398@e103592.cambridge.arm.com>
Date:   Tue, 4 Jun 2019 10:57:14 +0100
From:   Dave Martin <Dave.Martin@....com>
To:     Viresh Kumar <viresh.kumar@...aro.org>
Cc:     Vincent Guittot <vincent.guittot@...aro.org>,
        Marc Zyngier <marc.zyngier@....com>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        linux-kernel@...r.kernel.org, kvmarm@...ts.cs.columbia.edu,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH] KVM: arm64: Drop 'const' from argument of vq_present()

On Tue, Jun 04, 2019 at 03:01:53PM +0530, Viresh Kumar wrote:
> On 04-06-19, 10:26, Dave Martin wrote:
> > I'm in two minds about whether this is worth fixing, but if you want to
> > post a patch to remove the extra const (or convert vq_present() to a
> > macro), I'll take a look at it.
> 
> This patch already does what you are asking for (remove the extra
> const), isn't it ?

Yes, sorry -- I didn't scroll back far enough.

> I looked at my textbook (The C programming Language, By Brian W.
> Kernighan and Dennis M. Ritchie.) and it says:
> 
> "
> The const declaration can also be used with array arguments, to
> indicate that the function does not change that array:
> 
> int strlen(const char[]);
> "
> 
> and so this patch isn't necessary for sure.

This is an array to which a pointer argument points, not an array
argument.  I think that's how we hit the constified double-indirection
problem.

Cheers
---Dave