Re: [PATCH 2.6.6] bootmem.c cleanup

H. Peter Anvin
2004-05-17T00:43:55Z

Followup to: <20040514133353.236acf3a.akpm@osdl.org>
By author: Andrew Morton <akpm@osdl.org>
In newsgroup: linux.dev.kernel
>
> Michael Buesch <mbuesch@freenet.de> wrote:
> >
> > - if (!test_and_clear_bit(i, bdata->node_bootmem_map))
> > - BUG();
> > + BUG_ON(!test_and_clear_bit(i, bdata->node_bootmem_map));
>
> Please don't put expressions whihc actually change state inside BUG_ON().
> Someone may decide to make BUG_ON() a no-op to save space.
>
> I'm not aware of anyone actually trying that, but it's a good objective.
>

If so they should make it:

#define BUG_ON(x) ((void)(x))

.. which preserves side effects while generating no object code for a
side-effect-free expression.

The only reason for the cast to (void) at all is to keep gcc from
complaining about an ignored expression.

-hpa