linux-kernel - Re: [PATCH] [4/23] pagemap: Avoid unused-but-set variable

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Date:	Sat, 19 Jun 2010 09:44:13 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] [4/23] pagemap: Avoid unused-but-set variable

> urgh.  In fact I'd urgh the whole patchset.
> 
> Problem is, anyone who looks at all these random (void) casts is going

There are actually not that many in the patch kit if you read it 
completely. I think that's nearly the only one outside a macro.

> to have a hard time working out why they're there.  This is worsened by
> the long-standing practice wherein some people put unneeded (void) casts all
> over the place due to being traumatised by lint 15 years ago (I think).

It's really the same reason why they used this with lints.

When I tried it first I started complaining about gcc too (I even
filled a gcc bug), then disabled it in my build,
but after some contemplation I found it really finds real bugs.

> 
> Wouldn't it be better to make this stuff self-documenting, so anyone
> who reads the code can immediately see what it's doing, rather than
> scratching their heads over random, seemingly-unneeded casts?
> 
> #define gcc_46_is_a_pita(expr)	((void)(expr))

The warning is really useful and we'll get all used to it.

So I went with the plain cast. Maybe some more comments would
be useful.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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