linux-kernel - Re: [patch 01/10] compiler: define __attribute_unused_

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Date:	Tue, 1 May 2007 23:25:38 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Rusty Russell <rusty@...tcorp.com.au>
cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 01/10] compiler: define __attribute_unused__

On Tue, 1 May 2007, David Rientjes wrote:

> The patched version makes this:
> 
> 	int type __attribute_unused__ = 0;
> 
> which definitely tells you that you're using a compiler attribute that 
> will be attached to that automatic.  In your case:
> 
> 	int type __unneeded = 0;
> 
> doesn't say anything in this case.  It doesn't resemble any attribute that 
> a programmer might be familiar with and begs the question of why we've 
> declared it if it's truly "unneeded"?
> 

One possible way to remedy this situation is with __needed and 
__maybe_unneeded.

__needed would be defined to __attribute__ ((used)), which would apply to 
functions only and specify that its code needs to be emitted anyway even 
though it appears to be unreferenced.  This is needed for gcc >=3.4.  In 
gcc <3.4, this gets defined to be __attribute__ ((unused)) to simply 
suppress the warning.  So now all functions that are unreferenced except 
in inline assembly get __needed appended.

__maybe_unneeded would be defined to __attribute__ ((unused)).  It can 
apply to either functions or variables to suppress the warning if they are 
unused.
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