linux-kernel - Re: [patch] use __asm__ and __volatile_

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Date:	Mon, 18 Jun 2007 08:27:15 -0600
From:	Robert Hancock <hancockr@...w.ca>
To:	David Woodhouse <dwmw2@...radead.org>
Cc:	Arnd Bergmann <arnd@...db.de>,
	Arjan van de Ven <arjan@...radead.org>,
	Mike Frysinger <vapier@...too.org>, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, linux-s390@...r.kernel.org,
	rmk@....linux.org.uk
Subject: Re: [patch] use __asm__ and __volatile__ in i386/arm/s390 byteorder.h

David Woodhouse wrote:
> On Mon, 2007-06-18 at 01:24 +0200, Arnd Bergmann wrote:
>> On Monday 18 June 2007, Arjan van de Ven wrote:
>>> On Sun, 2007-06-17 at 18:33 -0400, Mike Frysinger wrote:
>>>> This changes asm() to __asm__() and volatile to __volatile__ so that these
>>>> headers can be used with gcc's -std=c99.
>>> hmm but the kernel doesn't use -std=c99...
>> The byteorder headers are exported to user space through
>> include/asm-generic/Kbuild.asm, and they are used by a number
>> of other exported headers, so they should work with any
>> gcc flags that a user might want to use. 
> 
> Even those headers which are exported are _still_ kernel headers¹. The
> 'caveat emptor' principle still applies to them, and we don't have to be
> _that_ anal about it. GNU extensions (and proper C types, for that
> matter) should be acceptable, surely?

If we expect userspace apps to include them, then I would vote for no, 
not for anything outside of #ifdef __KERNEL__ in exported headers. Keep 
in mind also that C++ apps may need to include these as well and those 
extensions don't always play well in C++ mode. (Last instance I ran into 
was the ioctl argument checking macros _IOR, _IOW, etc. that create 
non-compiling code if you use them in a C++ program.)

-- 
Robert Hancock      Saskatoon, SK, Canada
To email, remove "nospam" from hancockr@...pamshaw.ca
Home Page: http://www.roberthancock.com/

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