netdev - Re: [Patch net-next] net: clean up skb headers code

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Message-ID: <20130530122459.GE2475@ritirata.org>
Date:	Thu, 30 May 2013 14:24:59 +0200
From:	Antonio Quartulli <ordex@...istici.org>
To:	David Laight <David.Laight@...LAB.COM>
Cc:	Ben Hutchings <bhutchings@...arflare.com>,
	David Miller <davem@...emloft.net>, amwang@...hat.com,
	netdev@...r.kernel.org, horms@...ge.net.au
Subject: Re: [Patch net-next] net: clean up skb headers code

On Thu, May 30, 2013 at 01:22:14PM +0100, David Laight wrote:
> > Of course - we need to look at the value that ALL_ONES()
> > generates in an expression. So the test print needs to be:
> > 	printf("%hhx %hhx %hx %hx %x %x %lx %lx %llx %llx\n",
> > 		ALL_ONES(a), ALL_ONES(b), ALL_ONES(c), ALL_ONES(d),
> > 		ALL_ONES(e), ALL_ONES(f), ALL_ONES(g), ALL_ONES(h),
> > 		ALL_ONES(i), ALL_ONES(j));
> > which then gives 0xffffffff for the first 4 entries.
> 
> Except I copied the wrong format line :-( It should be:
>  	printf("%x %x %x %x %x %x %lx %lx %llx %llx\n",
>  		ALL_ONES(a), ALL_ONES(b), ALL_ONES(c), ALL_ONES(d),
>  		ALL_ONES(e), ALL_ONES(f), ALL_ONES(g), ALL_ONES(h),
>  		ALL_ONES(i), ALL_ONES(j));

Oh ok, I see the issue now.

So the problem is that this value gets bigger than what the maximal
value for the type passed as argument is supposed to be.

I think the issue is clear now and why a double cast is good.

Cheers,


-- 
Antonio Quartulli

..each of us alone is worth nothing..
Ernesto "Che" Guevara

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