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Date: Thu, 16 Oct 2003 07:55:31 -0700
From: Andrew Morton <akpm@osdl.org>
To: Ingo Oeser <ioe-lkml@rameria.de>
Cc: zwane@arm.linux.org.uk, linux-kernel@vger.kernel.org
Subject: Re: [PATCH][2.6] constant_test_bit doesn't like my gcc
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Ingo Oeser <ioe-lkml@rameria.de> wrote:
>
> On Thursday 16 October 2003 06:22, Zwane Mwaikambo wrote:
> > On Wed, 15 Oct 2003, Andrew Morton wrote:
> > > >   static __inline__ int constant_test_bit(int nr, const volatile
> > > > unsigned long * addr) {
> > > >  -	return ((1UL << (nr & 31)) & (((const volatile unsigned int *)
> > > > addr)[nr >> 5])) != 0; +	return ((1UL << (nr & 31)) & (addr[nr >> 5]))
> > > > != 0;
> > > >   }
> > >
> > > Looks fine.  Does your compiler get this right?
> >
> > Yep, thanks.
> 
> Sorry, but I still don't get, what a "const volatile" is supposed to mean.

const: this function doesn't alter it

volatile: someone else does modify it, so the compiler needs to avoid
caching it in a register.