linux-kernel - Re: "eliminate warn_on_slowpath()" change causes many gcc-3.2.3 warnings

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Message-ID: <alpine.LFD.2.00.0901181032350.3006@localhost.localdomain>
Date:	Sun, 18 Jan 2009 10:37:22 +1100 (EST)
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Kyle McMartin <kyle@...radead.org>
cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Mikael Pettersson <mikpe@...uu.se>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: "eliminate warn_on_slowpath()" change causes many gcc-3.2.3
 warnings



On Sat, 17 Jan 2009, Kyle McMartin wrote:
> 
> How about something utterly evil? (Since you can't pass a zero-length
> string to a printf attributed function either...)

Don't do this. That just forces a load off a complex pointer instead, with 
no upsides. At least if it was

	extern const char warn_slowpath_nofmt[];

it would only load the pointer itself, which is still a fairly  expensive 
op, but at least doesn't require the extra memory load.

But you'd be better off jusst making it something like

	#define NO_FMT ((const char *)(-1))

instead, which is really much more obvious, and doesn't need any of that 
"get a pointer" overhead.

		Linus
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