Re: Rep Spec Report with ASIS

[dewar@gnat.com (Robert Dewar)]

"John Cupak" <Jcupak744@mediaone.net> wrote in message news:<PMS68.69384$Ln2.15233029@typhoon.ne.mediaone.net>...
> 
> So, I thought that there might be an ASIS program someone out there in
> "Ada Land" has written that might provide the information requested. I would
> think it wouldn't be terribly hard to walk throught the declarations, find
> record
> type definitions, and generate a Representation Specification Report for
> each
> one - would it?

It would be virtually impossible unless the ASIS port you
are using supports the data representation section of the
ASIS standard, and this support is of course keyed to a 
particular compiler. However, as far as I know, ASIS-for-GNAT is the
only implementation of ASIS that
supports this optional capability.

The reason that this is virtually impossible is 

a) you would have to duplicate the entire data layout algorithms of
the compiler you are using, these algorithms
are often extremely extensive and complex.

b) you would have to know what these algorithms are. I don't think any
compiler has sufficiently complete documentation to reliably duplicate
the data layout for
this purpose.

We find that the -gnatR report that GNAT Pro can provide is
extremely useful, and a number of our customers very much
rely on this tool. The advantage here is that the compiler
is generating this information directly from the internal
data structures after laying out the data, so the output
from -gnatR is by definition exactly correct.

So basically you are out of luck here if you are not using
GNAT. Why not talk to your vendor and see if they can do
something for you -- perhaps they have some equivalent
internal tools that they can be persuaded to cough up.

(I say that because we find -gnatR enormously useful for
our support activities, and it is hard for me to imagine
how one would deal with things if you could not easily
tell how the compiler was laying things out).

Robert Dewar
Ada Core Technologies