Re: [sv-cc] Version 2 of DPI LRM] - compatibility, C Layer

Subject: Re: [sv-cc] Version 2 of DPI LRM] - compatibility, C Layer
From: Michael Rohleder (michael.rohleder@motorola.com)
Date: Thu Mar 13 2003 - 13:50:03 PST

Andrzej,

thanks a lot for this work.

I fully agree to John's comment.

Would it be possible to just add one more sentence that denotes that source code compatibility will/must not be compromised when using only canonical representation? I am unsure what is the best place within this paragraph.

The ideal statement for me would be something like this:
If you only do a), b), c) then binary/source code compatibility is guaranteed. When you do d), e) you might achieve better performance, but compromise the compatibility of your code. Your text is very near to this (especially when adding the comments John requested), but I had to read it three times to understand it (this might be caused by the actual state of my brain, it is not necessarily a problem of the text - I am unable to judge this now)

Best regards,
-Michael

Andrzej Litwiniuk wrote:

> Doug, JohnS, Michael and team,
>
> Would the following phrasing be less controversial and more precise?
>
> [ A.7.1 Overview - 3rd paragraph - C Layer of DPI]
>
> "Access to packed arrays via canonical representation involves copying arguments and does incur some overhead, however. Alternatively, for the sake of performance the application can be tuned for a particular tool and access the packed arrays directly through pointers using implementation representation, which could compromise compatibility. Data can be, however, moved around (copied, stored, retrieved) without using canonical representation while preserving binary or source level compatibility at the same time. This is possible by using pointers and size of data and when the detailed knowledge of the data representation is not required."
>
> Regards,
> Andrzej
>
> > --------------------------------------------
> > A.7.1 Overview - 3rd paragraph
> >
> > I'm a little confused by the wording of this. If applications
> > access packed arrays directly using implementation
> > specific representation, is it not also source compatiblity
> > that compromised as well ?
> >
> > Perhaps here we should make it clear that source compatability
> > is compromised in addition binary compatibility.
> >
> > I understand that if all access is done using the access
> > functions in section 10 for individual elements then it is
> > still source compatible. But the wording of this implies
> > direct access of the implementation specific representation
> > without using any functions but rather vendor specific
> > data types used in implementation. Was that your intent here ?
> >
> > -------------------------------------------- 

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