Re: 2.4.27-pre2: tg3: there's no WARN_ON in 2.4

[Adrian Bunk]

On Wed, May 12, 2004 at 12:07:44AM +0000, H. Peter Anvin wrote:
> Followup to:  <20040506121302.GI9636@xxxxxxxxx>
> By author:    Adrian Bunk <bunk@xxxxxxxxx>
> In newsgroup: linux.dev.kernel
> > > >
> > > >yep. Either we backport WARN_ON ;) or simply do the attached.
> > > >
> > > >--- old/drivers/net/tg3.c	2004-05-04 14:30:22.000000000 +0200
> > > >+++ new/drivers/net/tg3.c	2004-05-04 14:49:58.000000000 +0200
> > > >@@ -51,6 +51,10 @@
> > > > #define TG3_TSO_SUPPORT	0
> > > > #endif
> > > > 
> > > >+#ifndef WARN_ON
> > > >+#define	WARN_ON(x)	do { } while (0)
> > > >+#endif
> > > 
> > > Related but off topic. Do people find the ab#define	WARN_ON(x)
> > > a macro acceptable? The fact is that not mentioning 'x' means any
> > > side-effects are not executed, meaning the author must take special
> > > care when using this macro.
> > >...
> > 
> > Do not use code with side effects in BUG_ON and WARN_ON.
> > 
> 
> Why not use the much simpler:
> 
> #ifndef WARN_ON
> # define WARN_ON(x) ((void)(x))
> #endif
> 
> Preserves side effects and everything.

AFAIR, the -tiny tree already implements some kind of empty 
BUG/PAGE_BUG/WARN_ON macros.

When optimizing for size that way, your suggestion would result in 
bigger code.

And after a quick view, I haven't seen any WARN_ON users in 2.6 that
seem to rely on side effects.

> 	-hpa

cu
Adrian

-- 

       "Is there not promise of rain?" Ling Tan asked suddenly out
        of the darkness. There had been need of rain for many days.
       "Only a promise," Lao Er said.
                                       Pearl S. Buck - Dragon Seed

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