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

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Date:	Fri, 26 Mar 2010 14:04:08 -0700 (PDT)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	David Daney <ddaney@...iumnetworks.com>
cc:	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
	linux-arch@...r.kernel.org
Subject: Re: [PATCH] Protect prefetch macro arguments.



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.

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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