linux-kernel - Re: [PATCH] Protect prefetch macro arguments.

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Date:	Fri, 26 Mar 2010 14:18:05 -0700
From:	David Daney <ddaney@...iumnetworks.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH] Protect prefetch macro arguments.

On 03/26/2010 02:04 PM, Linus Torvalds wrote:
>
>
> On Fri, 26 Mar 2010, David Daney wrote:
>>
>> The GCC built-in __builtin_prefetch() is a vargs function.  If we
>> don't wrap the macro parameter in parentheses, a comma operator in the
>> actual argument list might cause unintended parameters to be passed to
>> __builtin_prefetch().
>
> This seems totally pointless and actively wrong.

Pointless, perhaps.  But 'actively wrong'?  Are you sure about that?

In any event I guess I don't care much one way or the other.  I was 
working on something else when I saw this. It looked wrong to me.

Thanks,
David Daney


>
> You cannot have a comma operator in the actual argument list to the
> #define, because if you did, then you'd get a
>
> 	macro "prefetch()" passed 2 arguments, but takes just 1
>
> so the only way I see to pass a comma operator is to _already_ have the
> macro parameter in parenthesis.
>
> 		Linus

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