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

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Message-ID: <Pine.LNX.4.64.0705012336430.22339@chino.kir.corp.google.com>
Date:	Tue, 1 May 2007 23:41:34 -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 Wed, 2 May 2007, Rusty Russell wrote:

> OTOH, your point about "__unneeded" is well taken.  "__needed" and
> "__optional" perhaps?  But their feature is *exactly* that the don't
> look like the gcc attributes, hence avoid their semantic screwage.
> 

Hmm, __optional doesn't sound appropriate either.  Since this is going to 
be defined to be __attribute__ ((unused)), it can apply to both functions 
and variables.  It should be applied to a function if it truly is 
unreferenced within the tree (and there are several examples of this 
current HEAD) and we don't want to use __needed because it still emits the 
function code even though it suppresses the warning.  So saying a function 
that has no callers is "__optional" makes no sense since its code isn't 
going to be emitted in gcc >=3.4.

What's your opinion of my __needed and __maybe_unused idea such as the 
following?

compiler: define __maybe_unused

Define __maybe_unused to apply to both functions or variables as
__attribute__((unused)).  This will not emit a compile-time warning when
a function or variable is declared but unreferenced.

We eventually want to change the name of __attribute_used__ to __used.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 include/linux/compiler-gcc.h |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -37,3 +37,4 @@
 #define  noinline			__attribute__((noinline))
 #define __attribute_pure__		__attribute__((pure))
 #define __attribute_const__		__attribute__((__const__))
+#define __maybe_unused			__attribute__((unused))
-
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