linux-kernel - Re: [PATCH -next] mm: fix set but not used warning

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Message-Id: <20190220134345.e39094996c111be4ffa0c976@linux-foundation.org>
Date:   Wed, 20 Feb 2019 13:43:45 -0800
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     "Kani, Toshi" <toshi.kani@....com>
Cc:     "yuehaibing@...wei.com" <yuehaibing@...wei.com>,
        "cpandya@...eaurora.org" <cpandya@...eaurora.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        "will.deacon@....com" <will.deacon@....com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "kernel-janitors@...r.kernel.org" <kernel-janitors@...r.kernel.org>
Subject: Re: [PATCH -next] mm: fix set but not used warning

On Tue, 19 Feb 2019 18:28:30 +0000 "Kani, Toshi" <toshi.kani@....com> wrote:

> On Mon, 2019-02-18 at 13:57 +0000, YueHaibing wrote:
> > Fixes gcc '-Wunused-but-set-variable' warning:
> > 
> > lib/ioremap.c: In function 'ioremap_page_range':
> > lib/ioremap.c:203:16: warning:
> >  variable 'start' set but not used [-Wunused-but-set-variable]
> > 
> > flush_cache_vmap may no need param, so add __maybe_unused fix this warning.
> 
> I think flush_cache_vmap should have a proper prototype with
> __maybe_unused for its args.  But, there are so many arch-specific
> definitions at glace, and I am not sure how manageable such change is,
> though...

This is one of the reasons why things like flush_cache_vmap() should
be implemented as static inline C functions, not as macros.