From: ganesh.ramasivan@gdcanada.com (Ganesh Ramasivan)
Subject: Re: Variant Record Sizes..
Date: 20 Aug 2004 07:09:28 -0700
Date: 2004-08-20T07:09:28-07:00 [thread overview]
Message-ID: <e8f9995c.0408200609.47f94a8b@posting.google.com> (raw)
In-Reply-To: cg2v3f$73h$1@sparta.btinternet.com
Thanks a lot for all your suggestions.
I found that the result is compiler dependent. On the GNAT compiler,
the size of Test_Record is 2 bytes but on the Greenhills Ada compiler,
the result is 4 bytes.
On consulting with Greenhills, they mention the following:
"The size of the record includes the size of the largest variant
part".
This would confirm the results I am getting with the GHS compiler.
Cheers!!
Ganesh
"Martin Dowie" <martin.dowie@btopenworld.com> wrote in message news:<cg2v3f$73h$1@sparta.btinternet.com>...
> Ganesh Ramasivan wrote:
> > Hello,
> >
> > I am having a hard time understanding variant records with regard to
> > memory usage. Does the size of the record become the size of the
> > largest element in that record?
> >
> > So in case of the example below, is the size of the Test_Record 2
> > bytes, even though the "use 8" clause has been specified as the other
> > element of the record specifies "use 16".
> >
> > Any input will be appreciated.
>
> Couple of things:
> Test_Record : TEST_ICP_POI_MESSAGE_TYPE(STATE_1);
>
> Constrains "Test_Record" to always be a subtype of TEST_ICP_POI_MESSAGE_TYPE
> constrained to "STATE_1".
>
> Because you didn't supply a default value to the descriminant you can never
> change which variant you want Test_Record to be:
>
> Both these things mean that the compile 'knows' that Test_Record need only
> be 2 bytes long.
>
> So,
>
> 1) Add a default to the descriminant if you every what to change which
> variant you want the variable to take; and
> 2) Don't constrain the variable at declaration time.
>
> Cheers
>
> -- Martin
next prev parent reply other threads:[~2004-08-20 14:09 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-08-19 18:48 Variant Record Sizes Ganesh Ramasivan
2004-08-19 19:29 ` Martin Dowie
2004-08-20 14:09 ` Ganesh Ramasivan [this message]
2004-08-19 19:30 ` Jeffrey Carter
replies disabled
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox