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bug#9157: [PATCH] dd: sparse conv flag

From: Paul Eggert
Subject: bug#9157: [PATCH] dd: sparse conv flag
Date: Tue, 28 Feb 2012 15:39:38 -0800
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:10.0.1) Gecko/20120209 Thunderbird/10.0.1

On 02/28/2012 03:13 PM, Jim Meyering wrote:
>> -#define OUTPUT_BLOCK_SLOP (page_size - 1)
>> > +#define OUTPUT_BLOCK_SLOP MAX (sizeof (uintptr_t), page_size - 1)
> I haven't seen justification for why you're making the above change.
> Can sizeof uintptr_t really be larger than page_size-1 (getpagesize()-1)?
> This seems so unlikely that it'd deserve an assertion in main where
> page_size is set, even though there are only two uses of OUTPUT_BLOCK_SLOP.

Theoretically getpagesize could return 1, no?
Admittedly it's unlikely.  I guess it'd be OK
to omit this change, and to just put in a comment
saying something like "We use the output slop
to store a uintptr_t value, so we assume that
getpagesize returns a value greater than sizeof (uintptr_t)."
Perhaps the comment should go right next to the place where
the uintptr_t sentinel is inserted.

> If you leave the sizeof, please omit the parentheses.

But "sizeof uintptr_t" wouldn't work, as uintptr_t is a type.

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