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Re: [Xen-devel] RFC: 32 bits as smallest atomic size.

To: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Subject: Re: [Xen-devel] RFC: 32 bits as smallest atomic size.
From: Keir Fraser <Keir.Fraser@xxxxxxxxxxxx>
Date: Sun, 27 Mar 2005 12:19:14 +0100
Cc: xen-devel@xxxxxxxxxxxxxxxxxxxxx, "Ronald G. Minnich" <rminnich@xxxxxxxx>, Jimi Xenidis <jimix@xxxxxxxxxxxxxx>
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On 27 Mar 2005, at 11:56, Keir Fraser wrote:

I don't think there are that many gcc-isms, apart from use of PACKED (please correct me if I'm wrong). You can always define that to nothing if you need to - I'd hope that no compiler adds padding since all fields should be naturally aligned. I don't see us moving to a model where we define macros on char arrays anytime soon. :-) But perhaps we could include a script to generate such macros from our structure definitions....

Actually this would get round the need to manually determine field offsets -- we could get rid of PACKED, let fields fall as they may, and then run the headers through gcc to get field offsets for those who need them. There are a very few cases where we actually really care about two fields being directly adjacent, but I could add annotations in the header files and run a script to check that the placement constraints are satisfied.

Already the field offset comments are broken in a few places in unstable, so perhaps this is a better way to go.

 -- Keir

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