linux-kernel - Re: [GIT PULL -tip] fix 41 'make headers

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Date:	Sun, 18 Jan 2009 18:29:08 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Sam Ravnborg <sam@...nborg.org>
Cc:	Jaswinder Singh Rajput <jaswinder@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	x86 maintainers <x86@...nel.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [GIT PULL -tip] fix 41 'make headers_check' warnings


* Sam Ravnborg <sam@...nborg.org> wrote:

> On Sun, Jan 18, 2009 at 01:57:22PM +0100, Sam Ravnborg wrote:
> > On Sun, Jan 18, 2009 at 12:02:21PM +0100, Ingo Molnar wrote:
> > > 
> > > * Jaswinder Singh Rajput <jaswinder@...nel.org> wrote:
> > > 
> > > > diff --git a/include/linux/acct.h b/include/linux/acct.h
> > > > index 882dc72..a20c97c 100644
> > > > --- a/include/linux/acct.h
> > > > +++ b/include/linux/acct.h
> > > > @@ -59,9 +59,13 @@ struct acct
> > > >  	comp_t		ac_majflt;		/* Major Pagefaults */
> > > >  	comp_t		ac_swaps;		/* Number of Swaps */
> > > >  /* m68k had no padding here. */
> > > > -#if !defined(CONFIG_M68K) || !defined(__KERNEL__)
> > > > +#ifdef __KERNEL__
> > > > +#ifndef CONFIG_M68K
> > > >  	__u16		ac_ahz;			/* AHZ */
> > > > -#endif
> > > > +#endif /* CONFIG_M68K */
> > > > +#else /* __KERNEL__ */
> > > > +	__u16		ac_ahz;			/* AHZ */
> > > > +#endif /* __KERNEL__ */
> > > 
> > > that looks rather ugly.
> > > 
> > > Why not just flip it around to:
> > > 
> > > 	#if !defined(__KERNEL__) || !defined(CONFIG_M68K)
> > > 
> > > ? Does headers_check misinterpret that?
> > 
> > The original expression is misinterpreted by headers_check
> > because we want the ac_ahz to stay if either of __KERNEL__
> > or CONFIG_M68K is not defined.
> > And unifdef does not optimize away the !defined(CONFIG_M68K)
> > part - it has no knowledge that this is kernel internal.
> > 
> > So I am happy with Jaswinder's patch.
> Almost happy.
> I digged out my original patch and it looks like this:
> -#if !defined(CONFIG_M68K) || !defined(__KERNEL__)
> +#ifndef __KERNEL__
>         __u16           ac_ahz;                 /* AHZ */
> +#else
> +  #ifndef CONFIG_M68K
> +       __u16           ac_ahz;                 /* AHZ */
> +  #endif
>  #endif
> 
> The indention can be discussed..
> But the logic is simpler.

yes - that's the 3-block versus 2-block issue i mentioned to Jaswinder. 
(the first version duplicated the same thing into 3 places - while the 
logic only splits it in two)
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