linux-kernel - Re: [patch 1/5] Introduce _

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Date:	Sun, 6 Jan 2008 07:42:02 -0800
From:	Arjan van de Ven <arjan@...radead.org>
To:	Richard Knutsson <ricknu-0@...dent.ltu.se>
Cc:	linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
	heiko.carstens@...ibm.com, olof@...om.net, mingo@...e.hu,
	mpm@...enic.com
Subject: Re: [patch 1/5] Introduce __WARN()

On Sun, 06 Jan 2008 12:44:56 +0100
Richard Knutsson <ricknu-0@...dent.ltu.se> wrote:

> Arjan van de Ven wrote:
> > From: Olof Johansson <olof@...om.net>
> >
> > Introduce __WARN() in the generic case, so the generic WARN_ON()
> > can use arch-specific code for when the condition is true.
> >
> > Signed-off-by: Olof Johansson <olof@...om.net>
> > Cc: <linux-arch@...r.kernel.org>
> > Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
> > ---
> >
> >  include/asm-generic/bug.h |   17 +++++++++++------
> >  1 file changed, 11 insertions(+), 6 deletions(-)
> >
> > Index: linux-2.6.24-rc6/include/asm-generic/bug.h
> > ===================================================================
> > --- linux-2.6.24-rc6.orig/include/asm-generic/bug.h
> > +++ linux-2.6.24-rc6/include/asm-generic/bug.h
> > @@ -31,14 +31,19 @@ struct bug_entry {
> >  #define BUG_ON(condition) do { if (unlikely(condition)) BUG(); }
> > while(0) #endif
> >  
> > -#ifndef HAVE_ARCH_WARN_ON
> > +#ifndef __WARN
> > +#define __WARN() do
> > {							\
> > +	printk("WARNING: at %s:%d %s()\n",
> > __FILE__,			\
> > +		__LINE__,
> > __FUNCTION__);				\
> > +
> > dump_stack();
> > \ +} while (0) +#endif
> > +
> > +#ifndef WARN_ON
> >  #define WARN_ON(condition)
> > ({						\ int
> > __ret_warn_on = !!(condition);				\ 

> What about using a boolean for __ret_warn_on, which then let us
> remove the '!!'?

is iffy.. like what happens if an u64 is cast to a boolean?
No matter what the final assembly code will need to be the same

> (btw, wouldn't 'var != 0' actually be the proper semantic instead of 
> playing with '!'s?)

no because var could be a pointer for example...

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