linux-kernel - Re: sound/pci/asihpi/hpioctl.c:125:6: warning: cast to pointer from integer of different size

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Date:	Fri, 08 Feb 2013 09:06:52 -0800
From:	"H. Peter Anvin" <hpa@...ux.intel.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	kbuild test robot <fengguang.wu@...el.com>,
	Ville Syrjälä 
	<ville.syrjala@...ux.intel.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: sound/pci/asihpi/hpioctl.c:125:6: warning: cast to pointer from
 integer of different size

On 02/08/2013 07:28 AM, Russell King - ARM Linux wrote:
> 
> Whether that's safe for x86 or not, I don't know, but my suspicions are
> that it's unsafe on x86 as it's possible to refer to the various bytes/
> half-words of eax separately.
> 
> So, I came to the conclusion that if x86 remains a problem, there's
> little point supporting it on ARM.
> 

It is possible to access bytes separately, but gcc generally doesn't.
However, whether or not that can be relied upon safely is a tricky question.

It *is* also worth nothing that the x86 ABI does allow two words to be
returned in registers from a normal C function, simply by returning a
structure.  That doesn't solve the problem at hand, though, which is how
to make a type-neutral macro which can handle doublewords...

	-hpa

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