linux-kernel - Re: [PATCH] doc: volatile considered evil

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Message-ID: <alpine.DEB.0.99.0705091321470.26189@chino.kir.corp.google.com>
Date:	Wed, 9 May 2007 13:25:05 -0700 (PDT)
From:	David Rientjes <rientjes@...gle.com>
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
cc:	Randy Dunlap <randy.dunlap@...cle.com>,
	Satyam Sharma <satyam.sharma@...il.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Paul Sokolovsky <pmiscml@...il.com>,
	linux-kernel@...r.kernel.org, jeremy@...p.org
Subject: Re: [PATCH] doc: volatile considered evil

On Wed, 9 May 2007, Alan Cox wrote:

> arch/foo almost always supports a single compiler too - gcc. We simply
> don't support anything else. We use gcc inlines and features extensively.
> 

Ok, so your "acceptable use clause" of your addition should include that 
fact.  That the volatile type qualifier is legitimate when developing a 
new architecture and the only implementation you support for compilation 
of such text has a one-to-one correspondence between actual and abstract 
machine semantics.

> [1] ANSI C says access to the padding fields of a struct is undefined.
> ANSI C also says that struct assignment is a memcpy. Therefore struct
> assignment in ANSI C is a violation of ANSI C...
> 

Padding bytes are unspecified, not undefined.  I doubt ANSI C says 
padding bytes are undefined because then any implementation that pads 
members of a struct object would not be strictly conforming.

		David
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