linux-kernel - Re: [PATCH] ptrdiff_t is not uintptr

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Message-Id: <E83C36D0-B72E-4E70-BEF6-4AF54BAD2863@cam.ac.uk>
Date:	Mon, 20 Aug 2007 01:29:21 +0100
From:	Anton Altaparmakov <aia21@....ac.uk>
To:	David Brownell <david-b@...bell.net>
Cc:	Al Viro <viro@....linux.org.uk>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] ptrdiff_t is not uintptr_t, damnit

Hi,

On 20 Aug 2007, at 01:19, David Brownell wrote:
> On Sunday 19 August 2007, Al Viro wrote:
>> is wrong; for one thing, it's a bad C (it's what uintptr_t is for;  
>> in general
>> we are not even promised that ptrdiff_t is large enough to hold a  
>> pointer,
>
> ISTR we don't *have* a uintptr_t on all architectures, or that would
> be the appropriate thing to use in these 32/64 bit ABI scenarios.
>
>
>> Use unsigned long or uintptr_t instead.
>
> I suspect you mean "unsigned long long"...

No he doesn't.  "unsigned long" is guaranteed to be large enough to  
hold a pointer (at least on Linux anyway).

On a 32-bit arch "unsigned long" is 32-bit and pointers are 32-bit.

On a 64-bit archi "unsigned long" is 64-bit and pointers are 64-bit.

Best regards,

	Anton
-- 
Anton Altaparmakov <aia21 at cam.ac.uk> (replace at with @)
Unix Support, Computing Service, University of Cambridge, CB2 3QH, UK
Linux NTFS maintainer, http://www.linux-ntfs.org/


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