From: dennison@telepath.com
Subject: Re: win32ada design question/problem
Date: 1998/11/18
Date: 1998-11-18T00:00:00+00:00 [thread overview]
Message-ID: <72vjpm$ui9$1@nnrp1.dejanews.com> (raw)
In-Reply-To: 36531538.483857@SantaClara01.news.InterNex.Net
In article <36531538.483857@SantaClara01.news.InterNex.Net>,
tmoran@bix.com (Tom Moran) wrote:
> >I think a binding done with System.Address for pointers and strings, and
> >Interfaces.C.Int for integers, would be far better.
> Why exactly is X'Address preferable to X'Unchecked_Access?
> Having spent a fair amount of time in the past debugging/correcting
> supposedly portable code that incorrectly assumed an access type was a
> 'Address, I'm rather sensitive to this issue.
Its preferable philosophicly when I don't know and don't *care* what type of
object it points to, other than possibly its size. This is often the case in C
bindings and OS calls.
With access objects I have three choices:
o Write one binding for each C-routine/passed object combination I will
ever want to use.
Clearly unacceptable.
o Arbitrarily pick some dummy access type to use for the C-routine, and
convert other accesses and addresses into it.
In keeping with the C approach, but Evil. Can cause confusion for
maintainers and other readers, and thus may cause bugs in the future.
o Create and use some unconstrained data array access object. Not evil.
But unchecked conversion or address_to_access_conversion is still required to
get a value of this type. Careless attempts to dereference the pointer may
cause problems due to lack of bounds information. Way more work than using
Address.
--
T.E.D.
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next prev parent reply other threads:[~1998-11-18 0:00 UTC|newest]
Thread overview: 31+ messages / expand[flat|nested] mbox.gz Atom feed top
1998-11-13 0:00 win32ada design question/problem Mats Weber
1998-11-13 0:00 ` dennison
1998-11-16 0:00 ` Stephen Leake
1998-11-16 0:00 ` Tucker Taft
1998-11-17 0:00 ` dennison
1998-11-17 0:00 ` Mats Weber
1998-11-17 0:00 ` dennison
1998-11-17 0:00 ` Mats Weber
1998-11-17 0:00 ` Tucker Taft
1998-11-18 0:00 ` Tom Moran
1998-11-18 0:00 ` dennison
1998-11-13 0:00 ` Tom Moran
1998-11-16 0:00 ` Mats Weber
1998-11-18 0:00 ` Tom Moran
1998-11-18 0:00 ` dennison [this message]
1998-11-19 0:00 ` Mats Weber
1998-11-19 0:00 ` David Botton
1998-11-19 0:00 ` Mats Weber
1998-11-23 0:00 ` Marin David Condic
1998-11-19 0:00 ` dennison
1998-11-19 0:00 ` David Botton
1998-11-19 0:00 ` Mats Weber
1998-11-27 0:00 ` Roga Danar
-- strict thread matches above, loose matches on Subject: below --
1998-11-19 0:00 tmoran
1998-11-19 0:00 ` dennison
1998-11-19 0:00 ` Tom Moran
1998-11-20 0:00 ` dennison
1998-11-20 0:00 ` Tom Moran
1998-11-23 0:00 ` Marin David Condic
1998-11-23 0:00 ` Mats Weber
1998-11-24 0:00 ` dennison
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