From: "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>
Subject: Re: Direct_IO and files of tagged types
Date: Thu, 26 May 2005 20:22:38 +0200
Date: 2005-05-26T20:22:42+02:00 [thread overview]
Message-ID: <86bcmsy3e49m.yjhfcxtf7osr.dlg@40tude.net> (raw)
In-Reply-To: 1117128009.277967.14010@g14g2000cwa.googlegroups.com
On 26 May 2005 10:20:09 -0700, John McCormick wrote:
> When I instantiate a version of Ada.Direct_IO with an element type that
> is statically tagged (it is of a specific tagged type) GNAT gives me a
> warning that the element type contains an access value. My tagged type
> has three integer fields - no access types. I assume that the access
> type referenced in the warning is to the tag mechanism. Any suggestions
> for ways to create binary files of statically tagged objects?
It is not a good idea to write tags into a file even if they are statically
known, because that cannot be portable. Another general question is: if the
tag is always known what for to have it? Without dispatching tags are just
useless overhead!
Anyway what about:
1. Aggregation: you put a plain record into tagged type and do I/O with
that record.
2. A completely independent record type used for external representation of
tagged objects.
3. Handles/smart pointers: tagged objects refer to a plain record type via
an access discriminant or an access type.
--
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de
next prev parent reply other threads:[~2005-05-26 18:22 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-05-26 17:20 Direct_IO and files of tagged types John McCormick
2005-05-26 18:22 ` Dmitry A. Kazakov [this message]
2005-05-26 23:51 ` Randy Brukardt
2005-05-27 8:38 ` Dmitry A. Kazakov
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