GNU bug report logs - #9157
[PATCH] dd: sparse conv flag

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Message #64 received at 9157 <at> debbugs.gnu.org (full text, mbox):

From: Paul Eggert <eggert <at> cs.ucla.edu>
To: Jim Meyering <jim <at> meyering.net>
Cc: 9157 <at> debbugs.gnu.org, roman.rybalko <at> romanr.info,
	Pádraig Brady <P <at> draigBrady.com>
Subject: Re: bug#9157: [PATCH] dd: sparse conv flag
Date: Tue, 28 Feb 2012 15:39:38 -0800

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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