From: Keith Owens <kaos@sgi.com>
To: Paul Jackson <pj@sgi.com>
Cc: wli@holomorphy.com, colpatch@us.ibm.com, linux-kernel@vger.kernel.org,
       mbligh@aracnet.com, akpm@osdl.org, haveblue@us.ibm.com
Subject: Re: [PATCH] nodemask_t x86_64 changes [5/7] 
In-reply-to: Your message of "Thu, 25 Mar 2004 23:14:12 -0800."
             <20040325231412.2a3d1c15.pj@sgi.com> 
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Date: Mon, 29 Mar 2004 15:08:46 +1000
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On Thu, 25 Mar 2004 23:14:12 -0800, 
Paul Jackson <pj@sgi.com> wrote:
>Does your way work if NR_CPUS is less than BITS_PER_LONG?
>Won't gcc complain upon seeing something like, for say
>NR_CPUS = 4 on a 32 bit system:
>
>   { [ 0 ... -1 ] = ~0UL, ~0UL << 28 }
>
>with the errors and warnings:
>
>  error: empty index range in initializer
>  warning: excess elements in struct initializer

I only did one case, to concentrate on the value for the last word.  A
full implementation has to cater for NR_CPUS < BITS_PER_LONG as well.

>and shouldn't the last word be inverted: ~(~0UL << NR_CPUS_UNDEF) ?

For big endian, ~0UL << NR_CPUS_UNDEF is right.  For little endian, it
depends on how you represent an incomplete bit map.  Is it represented
as a pure bit string, i.e. as if the arch were big endian?  Or is it
represented as a mapping onto the bytes of the underlying long?

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